It has come lightyears.

ProtonDB has a feature where you can give it access to your Steam account for reading and it'll give you a full report based on your personal library: https://www.protondb.com/profile

And I find if anything it tends to the conservative. I've encountered a few things where it was overoptimistic but its outweighed by the stuff that was supported even better than ProtonDB said.

In the late 2000s, I played a few things, but I went in with the assumption it either wouldn't work, or wouldn't work without tweaking. Now I go in with the assumption that it will work unless otherwise indicated. Except multiplayer shooters and VR.