Which MMO?

I agree with this, not being able to install things globally or use other package managers like pip was really annoying. I didn’t spend that much time with it to be honest, but just simply trying to set up a dev environment wasn’t fun. Also I’m pretty sure elixir doesn’t work on nix at least when I tried it

You should check out path of exile 2 it seems like they might be addressing a lot of your concerns with the genere. And GGG (the makers of poe2) are actually a really good company to support