It's usable until it isn't. That's the problem with Wine/Proton. It's not a stable implementation of a well defined specification like Java. It's a reimplementation via reverse engineering of proprietary Win32, something that's buggy and sometimes changed between Windows updates by accident.

Update to a game compiled with a slightly newer version of Visual Studio, like it's happening all the time with live service games? Compatibility becomes a dice roll. Sure, the chance is high that compatibility is kept but it not 100%. Neither is Proton not breaking a game by accident. The big games are automatically checked by Valve but some weird indie game isn't.

And here comes the wonderful thing that's Steam Linux Runtime: containerized binary compatible runtimes of every other or so Debian release. All the issues about not being able to target Linux because of its ever changing nature have been fixed by Valve and yet for whatever reason Valve refuses to promote it towards developers.

They literally promote Win32+x86 emulation for Steam Frame development, a wearable platform where even the slightest stuttering can cause motion sickness and where battery optimization is paramount.

I hope Valve bring Lepton, their Android compatibility layer, to x86 Linux as well. Lepton is based directly on AOSP and not reverse engineering. I have higher hope for that.