Although I don't believe web hosting is the problem here. Anyone can build a server and have it accessed using his own IP. So censorship (by design or as a byproduct) would be hard to achieve (except DDoS obviously).
Registrar are a lot more relevant because they are a service that make internet addresses intelligible to humans. So preventing one from accessing this service (either by design or as a byproduct) is an hindrance to their ability to communicate more broadly the content of their server. Same goes with search engines BTW.
Also, there is another solutions worth exploring: decentralized DNS registration.
(I'm not aware of anything restricting me from setting up a server that answers DNS queries with quotes from Dune, it's just that, because I'm not following the convention, pretty much everyone would just ignore it)
I'm questioning whether entries stored on a particular set of DNS servers constitutes a medium.