I've been on a quite big mastodon instance for the local town (run by volunteers). When it was announced to shutdown I switched to a very small instance. And then problems where there: You don't see many posts because the small instance only imports posts from people followed by people on this instance. So you have to browse e.g. the giant mastodon.social for interesting content. And then try to follow the accounts from there.
Regarding political orientation: You'll find anything on some instances but that is also what fragments mastodon even further: Server admins block each other if they do not like the content coming from the other side.
On the other hand most of the interesting content I read on Nostr comes from mastodon. Most Nostr topics I see are still self centered or bitcoin. But it is not easy to interact with Mastodon content from Nostr. The mostr.pub relay does (of course) not copy all posts, is blocked by many instances. Also if I answer to a post from Nostr, it looks quite awkward on mastodon. Sometimes I switch to a mastodon client for that, but then again: Don't find the post in question on my instance, following via their home instance is complicated and it takes some time (sometimes days) to see the sought post then on my instance.