That's the current best alternative. Big studios are not going to invest development into a platform that does not directly translate to more money. Best they can do is make use of open APIs like Vulkan (Even tho DX11/12 work with the current tooling too).

I mean development on Windows got better by literally offering Linux through a subsystem. if you can't beat them, be them

The word emulating has a very specific meaning when playing a video game on one platform that was designed for another. If you are using the word emulating to mean something close to the word "mimic" or "imitate" then you are correct, but the word emulation shouldn't be used to describe proton because it is not an emulator in the way most gamers will understand. This point is specifically drilled into the Proton history. Proton is a fork of the Wine project. In 1993 (!) it was declared Wine is Not An Emulator. Recursive naming is an open source tradition.

Aside from being an incorrect use of jargon, it hurts the project. Emulators have a reputation of not being able to handle the latest games. Proton is very good at playing many modern games. It plays some games better than Windows natively on the same hardware.