You are not wrong.

The difference, in my opinion, is that reddit, etc are quite active in removing such "communities" once they are aware of them and they become a problem.

Parler does not. In fact, to me, it seems they take delight in it and promote it under the guise of "free speech".

So while reddit and co undoubtedly have similar problems they at least take action albeit a lot later than I think they should.