Nomadic identity is a bit of a weird one, because there’s no silver bullet. It’s either:

• People store their credentials and data on their own systems in a peer-to-peer like system, but people are going to be constantly losing their access to their identity if they do this, so while this is technically ideal, it isn’t going to work for those that aren’t too familiar with technology. People have gotten very used to not having to look after their data in recent years.
• The identity is handled by some sort of identity server for authorisation, but what this will most likely do is give rise to some centralised identity services that you’re going to have to trust, which arguably may be against decentralisation.

I do agree it would be way better for a single account/identity to just work everywhere on the Fediverse, but I’m not entirely sure how the details should be handled. Nostr is one implementation (it’s the first one), whereas things like SSO with Google / Microsoft is the second (kbin, for example, has this).

I have noticed that Mastodon development has slowed down considerably though, but admittedly it must be hard having requests from literally every angle about every use case and concern. It’s easy for us to say “just add quote posts”, “just add search”, but the people who have already been on Mastodon have used it knowing those don’t exist, so the Mastodon developers have to implement these things while still thinking of every use case and also still sticking to their own beliefs as to what Mastodon should be.