Well, I guess the key is that we need to be clear about what Fediverse does and doesn't promise.
It doesn't promise permanent operation of any particular instance, and it doesn't promise that history will be maintained forever.
You can rely on infrastructure for what it DOES promise; that just wasn't a feature it was promising.
(Personally, I really want people to realize that Fediverse doesn't promise privacy, as I think a lot of people are mislead on that, but that's a different topic)