I live in one country that could be next. Putin already has useful idiots here daying thay we should leave NATO. Putin also tried to push for these countries thay used to be in the Russian sphere of influence not to be in NATO.
You make one step back and Putin makes two forward.
So you are saying Mastodon won’t take off because people need to choose a server but also because having a “default” where majority will ptobably end up is bad - but this is literally the solution to the problem you mentioned