Moderators of highly restrictive instances (the most populous ones) blacklist all the instances they don't like. In fact most of those instances use a shared blacklist. So you have to make a choice: either you choose a restrictive instance and you can't talk about whatever you want (because with so many rules, where are they even drawing the line), or you go to a free instance and can't talk to anybody in the most populous instances (most of the network).
Or you simply get the best of both worlds and stay on Twitter.
Or you simply get the best of both worlds and stay on Twitter.