I used to think so too, but talking about it with a few friends that genuinely gave Mastodon a shot, I changed my mind.
Federation (not easily understandable) + Lack of users (and thus content) are the main reasons.
Federation (which Bluesky also strives to achieve) is not something that you’ll even notice once registered, and the lack of users (and thus content) is a self-fulfilling prophecy, don’t you think?
What I meant behind federation was that the registration process can be hard to understand. But you’re right, after passing this step, you don’t really notice federation.
As for the self fulfilling prophecy, I think you’re right, which is why I still try to nudge my friends towards mastodon / pixelfed. I still believe in these projects, but I also don’t think Bluesky will be too detrimental to their growth.