At the end of the day, Substack is a blog hosting platform too. A blog is far easier to self-host than any of these other things.
It's not really clear why someone really needs yet another middleman coming along here. It's even less clear when using that middleman involves getting dragged into that middleman's own political drama.
At the end of the day, someone just wants to host a blog. Why so many games?
Setting policies, quietly "reinterpreting policies" (to avoid the embarrassment of publicly backing down), these are like Big Tech shenanigans, and not particularly fun ones.
It's not even particularly good for free speech. The approach of the neutral hoster might be better (and would include things related to sex) than acting as if they're out there to save journalism.
It's also the sort of platform that is entirely optional.