Well, I imagine the easy fix would be to separate screen names from usernames. Like, you'd sign in with your shitty, number filled username, but you could set the actual name that appears to everyone else to be whatever you want, even if someone else already uses that name. Sure, this could lead to impersonation and shit, but plenty of sites like youtube already have verification type stuff, so I'm not sure it'd be that big of a deal.

Or maybe in the strange new future of 20XX, we'll all be forced by our supreme overlords to each have some semblance of originality

And thus the second Dark Ages will truly begin