I'm not familiar enough beyond casual use of Steam on Linux and a few one-offs to know the current state of gaming... but can only posit that a GoG installer/launcher for Linux that uses Proton (like Steam) wouldn't hurt.
It can run things with regular wine or proton installed by steam. There is a lot of complexity compared to Steam or the GOG client.
Why would i want to launch a seperate launcher to launch my games?