In my experience, it’s not actually Proton specifically but more generally Wine along with DXVK and Vulkan itself.

I have as good a success rate with Windows games from GOG under Wine through Lutris (which also defaults to using DXVK and Vulkan plus has Wine configuration scripts for most GOG games, making their install fully automated and zero-configuration) as I have with Windows games from Steam under Proton.

If I understand it correctly, Proton is mainly a fork of Wine with Steam integration thrown in and changes to make sure it works with specific Steam games, so I don’t think the improvements are Proton specific, but rather more global than that (the use of Vulkan instead of OpenGL, DXVK making DirectX games run with Vulkan, Wine improvements).

Mind you, if improvements in Proton are flowing to those other projects and having a big impact, then credit were credit is due for Proton pulling up the whole ecosystem, otherwise Proton isn’t actually as crucial in improving Gaming on Linux as seems to be portrayed in so many posts here.

I can understand that if all people have used for gaming in Linux is Steam and never games from other digital sources - like GOG or even pirated games - via launchers like Heroic or Lutris, it might seem like Proton is the secret juice, but in my experience in the last year of gaming in Linux using both, Wine + DXVK + Vulkan works just as well.