The people behind this demo already said their publishing different languages and accents soon along with open models you can run yourself.

I can't speak to whether it's desirable or not, but this has been happening with the advent of radio, movies, and television for over a century. So, are we worse off now, linguistically-speaking, than then? Do we really even notice missing accents if we never grew up with them?

Getting that wrong in some languages e.g. Korean can be offensive.