I think the issue with mainstream mastodon discussion and adoption is several fold.

The first is that for a large chunk of the population the appeal of twitter is that it's full of famous people, big name professionals, industry insiders, journalists, local governments, and etc. Mastodon users will often brush this off as not why they enjoy microblogging, but a lot of mainstream users care a lot about this. Twitter is a service where you follow individuals not communities and topics and so if the people you follow arent on the replacement service it matters.

The second is that mastodon is over protective about pulling in posts and messages if nobody in that instance follows them which makes using mastodon a pain. The instance I subscribed to for example is federated with mastodon.social and many other major feeds but for some topics like say wrestling I have to open up another tab, and search on mastodon.social and then copy and paste stuff into the other tab. Its not necessarily unintuitive,but if we're already federated why arent I seeing these posts? Of course then I can fix this by following these people, but of course that doesnt pull over the old posts either so I still cant see their stuff on my instance unless they post something new.

Finally the community comes off as super defensive about the way things are. People get suggested this product(by mastodon users) as a twitter replacement and when they bring up potential usability and connection issues the community treats these people like theyre absolute morons. This might be more of a reddit issue, since I've googled some questions and complaints I had with mastodon and it took me there. The github is more civil but there doesnt seem to be appetite to make changes that would make it easier to follow or find people that are several instances removed from you. I know someone put it like "you dont have to be a part of every conversation" which works for message boards, and communities like reddit, lemmy, and such, but on a service that built to follow specific people it's a problem.