Is it a problem that people with a common interest, cannot find common ground ? Yes, it is a fatal flaw for a social network.

Sure, and client viewer can activate a "local posts only". It's easy to exclude everything else.

But you can't undelete what never existed. If there is no common space there is no community.

The best compromise Lemmy has is "the one big community" that drowns out everything and sucks the air out.