i think this might be a problem with many of the "replacement" services. That initial growth and boom was driven by the novelty and curiosity of the service. Now that twitter is seen as kind of played out it feels unnecessary to be on a clone of it. The draw is gone and most of the utility(alerts) have moved elsewhere.
i tried using bluesky and it just felt...lame? It wasn't really bluesky, just the fact I was on yet another social media service. A significant amount of folks on there are only on there because it isn't twitter. then they realize they don't need twitter which means they dont need bluesky.
bluesky feels like a bunch of high school kids who didnt get invites to the real prom so they made a different prom, but the different prom kinda sucks. "Yay, prom!" "Um..this isn't prom, this is different prom."