> There are four platforms that have a considerable number of users (TikTok, Youtube, Twitter, Facebook/Instagram), and they
all have provenly effective censorship, especially optimized over the past couple of years. If it's one of those four, it does matter.
Three of those platforms are American-controlled and one is Chinese-controlled. Even if all four have "effective censorship", it seems unlikely that American-controlled and Chinese-controlled platforms will block/manipulate in the same way and to the same end.
This is not a fixed set either – every few years, a new platform pops up. Tiktok is a relatively recent example, Instagram an earlier one.
If content restriction gets too heavy-handed, people will respond by moving to new platforms which are less restrictive – at least in free(-ish) countries. I personally think that inconsistent and overly heavy-handed moderation – punishing too many users by algorithm for innocent or trivial things, even while reports against other users doing seemingly much more serious things are dismissed – is one of the factors behind Facebook's recent slide in users.
Added to that, many people on the political right (30-40% of the population) view these platforms as politically biased against them, and are keen to find new places without that perceived bias. Attempts at establishing more conservative-friendly platforms generally come unstuck by being overrun by extremists (neo-Nazis, antisemites, etc) who push mainstream right-wing users away, and also through pure incompetence (both technical and business). But I think it is likely that sooner or later someone is going to come up with the right balance to succeed in that space.