Much of what you say is true. I wouldn't advocate buying a Trax or a Chevy-whatever for any price.
For me, poor dealership support is a minor issue. I spanner my cars because I believe I do a better job and I usually enjoy it.
I have always had a zero expectation from any interaction with a dealer.
Parts? Not worried. As
@Haakon has pointed out it's a global market. After a few years if/when supply dries up you get your google fu going (that's what I meant by "know what you're in for").
Your fears about depreciation are a non-issue
as long as you run the numbers and get the correct discount.
The discount IS the depreciation hit taken out. It doesn't matter how much it's worth in 3 years if you paid the right price.
You could actually be worse off paying more for a different brand and suffering slightly worse depreciation.
Yes, if you pay too much you will be worse off.
The other bonus is that if you're financing, the total interest will be less because the financed amount is lower.
....and as
@SummitFever pointed out, brand new is brand new. You can look after it from the start. Used cars are a lottery - and most people don't do enough maintenance.