I think it was Supergiant Games who said that because Proton is good enough, they're don't plan to provide native Linux versions of their games in the future.
Does the game run well in Proton? Then who cares if it’s not native. What’s wrong with using Windows APIs to run games on Linux? Let’s take Microsoft’s API, embrace it, and steal that sweet sweet gaming marketshare.
The other day I bought Ziggurat 2, a great game except for some mysterious input lag on the native version. Partially out of amusement, I tried playing it through Proton and poof, there went the latency. I do not know what kind of black magic it's using, but it seems to work quite well.
I think it's pretty much impossible now to create a modern game with the Steam runtime: