I see what you're saying about it not needing a standards body, and of course that can work fine, but for me it's an advantage that AP is maintained by a body independent from any specific implementation. An equivalent would be if the AP spec was defined by the Mastodon devs and community—not a bad thing, just not as good in my mind.
The relays thing I think was what the unable to really ban comes from. Are there moderation tools to propagate bans across relays quickly? Does nostr have the same issues as with lemmy instances where an admin abandons the relay and it gets overrun with shit? Some users need to be booted off the network entirely and swiftly sometimes, we've seen several cases of this in Lemmy already with users posting horrendous shit. I'd be concerned that one of my relays would lag on banning (timezone differences for moderators or whatever innocuous reason) and these users achieve their goal of more people seeing the shit they post. For some people this might trigger PTSD, which is why I say it would be a huge barrier to mass adoption until that issue is resolved.
The user portability aspect is the main advantage of it that I can see, and it looks like a pretty clever solution to the issue. Though personally speaking, I only really care about my subscription list, which I sync between two accounts already using my lemmy client. I understand some people might care more about the other stuff though (particularly on microblog platforms)