My impression is that Nostr use is increasing, not declining, but less of the interaction is aimed at the people with big npubs posting kind 1 and more at people like me, or people in the smaller accounts talking amongst themselves, or activity in other kinds.

My own interactions continue to increase. Maybe it's just that some user's are moving away from OnlyPrimal or putting more effort into selecting relays, so that they can actually see the rest of us.