I very quickly gave up and just used Lutris, copied someones settings/versions from Reddit and it worked, but I wasn't too happy. I _really_ wanted to try Diablo4, so I put up with it, but normally my patience for such things is pretty low.
I am not averse to messing around with things, I've got a pretty good idea of how things work in Linux. I've written my own .so files to fix bugs in closed source software using LD_PRELOAD. I just don't want to deal with that when gaming.
There's more to Steam than just the pre-configured proton. Their controller support stuff is top notch and so is the stream link/stream stuff. Not using steam would definitely make my experience worse.