My main account over there isn’t that old, but I’ve been using the site off/on for probably at least that long. I mainly was a reader/lurker over there for years as I didn’t really feel like posting as at the time almost everything I posted got downvoted for some reason. Then over time as I got older I cared less about that and started posting more. Last I checked I think my karma was 100,000-something.

IMO, the fact that there’s no desktop version (AFAIK) and they made it so difficult to discover new content, pages/people. etc., & how many of the users are probably just Instagram users who had accounts auto-added & have no interest in Threads, are the main reasons for the decline.