There are ways to address all of these problems if and when they occur.
I think one of Nostr's biggest contributions is its culture of pragmatism and speed. Do something simple, quickly that works instead of sitting around worrying about every edge case (which is a what a lot of "decentralized" projects do). If you have no apps and no one using them, none of the problems you mention exist. If you come up with something ridiculously complicated (think some recent w3c proposals), you've built a massive barrier to contributors and to developer and user adoption.