It's not "random". Some servers have legal concerns about the art they host, but also last I checked their moderation in general wasn't great (not sure if it was a "no english-speaking moderators" problem or a "we don't care" problem though.)

the reason is because pawoo and baraag are de-facto lolicon servers with neither the censorship requirements of pixiv or the content moderation of twitter. servers in different countries are going to have different laws and different cultural mores so you will no longer have the twitter model of curating the world's content by the standards of California progressivism which will probably also result in a far more fractured set of communities. considering the kinds of harassment artists are subject to on twitter, i don't even know if that is a bad thing.

Server blocks are not "random", and they are very much a part of how the fediverse functions. It's also what disincentivizes creating large effectively-unmoderatable instances, because you will very quickly find yourself isolated from the rest of the network. This is by design, not a bug - the fediverse is not meant to be a "town square".