I don’t think it’s that people want a monolithic platform? They just want a network that is big enough to provide enough new, high quality content to keep them amused/informed.
Back in the day this was a constant struggle for bulletin boards (the best of which were focused on a particular hobby or area of interest). Too small and the place was dead, often with a lot of poor quality content with no one around to correct it. Too big and it became impossible to moderate, and difficult to keep track of who was reliable and who was full of shit, and difficult to find what you were interested in if a handful of threads took off and pushed everything else out of sight.
After BBs mostly died, I used Twitter and Reddit as newsfeeds with informed commentary attached, plus bonus cute animal content. Mastodon and Lemmy/Kbin aren’t (yet) big enough to fulfill that role. Not enough of the commenters and sites I want to read stuff from are on it, and there are too few users to rely on to fill the gap.
At work, we want to switch. We use Mastodon and Twitter atm. But there are not (yet) enough specialists in our field in the fediverse for it to work. A small fediverse just can’t do the job we need it to do. (FWIW we’re public sector researchers; this is about disseminating research and finding collaborators, not advertising products.)
There is no one size fits all and neither should there be. The danger is that the small-is-good parts of the fediverse disappear because the content devolves to endless bitching about what other instances should have done and why won’t they all agree with us (even though we’re not a monolith, honest).