Well here's a can of worms that is very close to home. There are all sorts of issues in this thread and even some solutions. Sorry, this will be long to offer perspective.
Firstly not all benched trail is made by machine. We have made a lot of it or modified parts of some trails by benching into the hill, by hand. One of those was an illegal trail line built to replace a falline eroded disaster being ruined by illegal horse riding. That trail was always shit, but would fit the description of a minimalist trail with little modification to the natural terrain, something often quoted in support of old trails. In reality the meaning is all too often a deeply eroded, rocky, cupped, falline line without any natural rhythm.
On the Gold Coast the land manager (Qld Parks and Wildlife, not City of Gold Coast as many believe) does not like illegal trail. Nor does it like erosion. So when you have an existing network of eroded and illegal trail and a land manager that has previously ploughed trails back into the bush, you have to feel somewhat lucky when that land manager gives you the chance to remedy something they identify as their problem. More than erosion and illegal, they really dislike liability that (may) come from it. So, some years ago we started to work with QPWS with the goal of bringing all trails up to an acceptable standard (IMBA or QPWS alternative). The deal is we work through the park regions and move on when things are sustainable in a given region.
The biggest issues were in the region closest to the Nerang velodrome trailhead. In fact they were on the only legal MTB trails in the park - Three Hills Singletrack and Casuarina Grove, blue (intermediate) and Green (beginner) trails consecutively. Over the years we have worked with basically no help (sorry to those few who do help at times) to fulfil the requirements of our land manager by renovating and re-routing these trails. Three Hills is done now and Casuarina is sneaking towards being a decent beginner trail.
National parks have developed increasing ties with MTB, but they do like to have control over their parks. That includes a genuine fear for the nature of our sport (a fear not reduced when they see us ride) and an obligation to allow access for all (riders), especially families and beginners. Green trail by IMBA standards is 60-100cm in width with no exposure and no obstacle >20cm that does not have an alternate ride-around. Blue has tread generally 30-60cm and can have drops up to 60cm with ride-arounds. While that may sound like wide trail, that's the deal. Given the sideslope on parts of Three Hills is into the black (advanced) IMBA rating, there have to be compromises that cater to the land manager, the climate, local drainage and soil issues and a desire to finalise most tweaks within 6-12 months of opening the trail. We just don't have the manpower (budget is a different issue for volunteers) to keep coming back for ever.
So what do you get within these constraints? Well, we can offer technical trail features one trail grade higher so long as there are alternate lines. We can utilise the terrain as best we can allowing for the use of hand tools, but there is a limit to what can be done with respect to vegetation and time. A machine can create more imaginative lines fast, but that's not the sort of imagination this thread is about. What we cannot offer is trail so narrow you can't turn the pedals for fear of hitting the upslope and going over the edge, off the trail. We cannot stand with rangers at a section of deeply eroded, falline trail and call it "technical trail". We also cannot build more trail faster, because building new trail means closing old trail lines and doing that properly is slow and hard work.
What happens is we build, or repair, or modify trail and get shit from riders who never lift a fucking finger to help, ever. We get lip because we are doing what we are asked to and they think we are making sanitised trail. You cannot use a garden trowel to build trail on public land and to be honest, anyone that says they should or can is full of shit. A personal thank you goes to all the supporters and creators of illegal new trail in the park over the last 12 months - more time we get to waste when QPWS makes us close it up instead of making new trail! Building imaginative trail whether benched and green or narrow, rocky, nasty and black is hard work and takes experience. Taking responsibility for what you build is not familiar to a lot of people who build minimalist trail. Certainly in our national park the attitude is to fuck off and build another line of dog shit when the old one isn't good anymore. After spending 500+ hours (double that for my digging mate) a year for at least 7 years patching up such trail all over the park, it bugs me that people site those trails as evidence of how you don't have to build trail the new way because it lasts better if you build without building. Bullshit - we keep fixing it for you!
While I'd like to stick a pry bar up the arse of jerks who describe our work as too smooth and straight and wide as they hover over while you kneel in mud armouring a sodden creek crossing, it wouldn't make a difference. They will not see that it is trail requested within very limited constraints by the land manager. They will not see that it gets good riders out to more technical and old school trails (none of which are under threat unless built since 2012). They will not see that beginners are really the riders without trails in Nerang National Park. They will not see that 20 years ago, three riders per week used trails now used by hundreds a day. They will not see that when that happens immediately after massive rain events the effect on trails is very different to days gone by. They will not see, even if looking at it, that the trails are not smooth except in areas where the soil has no stone. They will not understand that trail starts smooth and then gets rough. They will not see that the riding line is narrowing over time and will continue to do so; or that you won't hit something by going off line when the grass grows back because the trail edge is cleared. They will whine about lack of challenge but not use the advanced lines, up or down. And they will not help get things done faster so we can get more imaginative with new trail lines, some that may actually be exactly what "we all like", because they prefer to ride the trails they whinge about and never work on them.
Then there's gravel. We had to add gravel into the surface of new trails during January and February in places where subsoil water bloats the trail from below. 1200mm of rain over 8 weeks on brand new trail (some hand and some machine made - we had our first ever professional building in late December) over the Summer holidays is too much for any new trail. Take a peak at some of the illegal trail and the results are pretty obvious. Lack of width and no attention to drainage is not the way to build trail and it is not resistant to rider and climate effects despite some vocal claims. When I hear of Buller trails being loose and gravelly and off camber (duh, everyone says they want that until they ride it), I remember reading that World Trail worked three times on the trails and then rested them for 3 months before opening. The new Nerang trails were ridden the day after completion, the day of opening and were poached continuously during construction. They had no hope of being perfect and didn't we cop a slagging from people out mashing them up in conditions that should have kept them home. So we added gravel selectively - barrowing it long distances by hand and tamping it in by hand. I don't like it and we will rake some away as it gets exposed, but if we hadn't done it the trails would have been hard to bring back after the rider and weather deluge of Summer.
Is there a solution? Yes and an obvious one. If you have a volunteer group in your area, get in touch. Don't just say what you want and why that removed rock was your favourite in the whole trail system; turn up to learn and learn to work. Here that means getting in touch with Gold Coast MTB Club - they have a trailcare afternoon tomorrow BTW. There are lots of ways to build and repair trail. It takes hard work and numbers make a difference - experienced numbers. If your interest is to scruff out some piece of shit track, don't do it in an area with legal trail building and a developing relationship with the land manager. If it means that much to you - buy your own land and assess your impact over time. Don't get me wrong - I see National Parks as our land and I am a strong advocate for MTB access. However, those who support scratching out illegal trail are doing harm and at least slowing progress for our sport. If you have time to complain and certainly if you have time to make illegal trail, then you have time to help. Until you are helping, the chances are you will not know why trailwork proceeds as it does. In our experience you can push the envelope gently and give riders good trails with challenge, but land managers have a limit and I can tell you that limit does not extend to having untended, eroded, trail that only 2% of riders are capable of riding and even less do.
Flow Trail is a cliche that should not have been used as an alternative for trail made to drain and avoid the issues of convoluted trail turning on itself with excessive falline. It is also not the modern alternative to more old school trail. They all have their place if made well and maintained as needed. The more minds and characters involved with volunteer trailcare, the better the chance for all to have trails they love. I agree with someone who said that love riding anything. So do I, but apparently that is not as common as the large, vocal group who only like the trail they had (and presumably rode it exactly the same way every time) until it was renovated back to the way it was when first opened. It's just that they cannot remember what the trail was like before the effects of riding, weather and time changed it and they feel they have to complain about all this modern flow shit.