The net result is that X shows breaking news, in the same way that the (infamous) meme of bullet holes marked on the WWII plane only shows part of the story - the people who have departed the platform aren't posting, and thus X is only breaking news from a subset of people.
This might be fine for certain types of topics. For understanding the zeitgeist on culture and politics, though, you can't filter your way towards hearing from voices that are no longer posting at all.