10-sp. officially is rated to a maximum 36T sprocket. The cage isn't the limiting factor, it's the upper body length and geometry. It can be cranked lower with the b-screw to gain more clearance, but because its shift path is optimised for the tighter cassette, as you shift to the middle & higher gears it gets further away from the sprockets than it's designed to be, which turns the shifting to shit because it allows the chain to flex more rather than shifting across. It gets worse as the chain wears. 42 is really about the biggest a 10-sp. can be coaxed into working on. Any bigger it's just not going to get the clearance without a goat link.
11-sp. derailleur isn't perfect because of the different leverage ratio, but it's close enough to be tweaked into reasonable functionality.