1. Nobody wants to maintain a generalist instance, partly because it's harder to apply generalist moderation policies and partly because it attracts so many more users.
2. Running your own instance does solve (1), but Mastodon was not designed as a P2P network and likely can't function that way.
I run my own and while my local feed is dead (even though I am not the only one on it), "home" and "federated" are fairly lively after following a few people.
i’m not sure what ya mean, the largest instance is generalist.
almost all of the most populated instances are also generalist:
mastodon.social
mastodon.cloud
mastodon.online
mstdn.social
mas.to
mastodon.world
and on and on.
there is no shortage of smaller generalist servers either.
i may be misunderstanding your larger point tho?