(this is a bit of a rant, i'm sorry)

what in particular do you mean by lack of discoverability?

like, i want to see posts from communities that i already subscribed to, but because there's more than 1000 communities on the fediverse and i'm only subscribed to a small countable subset of them, i inevitably lose out on a lot of content. (The "all" feed sucks unfortunately). So how to solve this?

The lack of discoverability is non-starter for many.

The Fediverse significantly lacks behind on the Content Discoverability technology.

I guess this is because there was a loud public outcry in the last 20 years that whoever makes your feed (this is called an "recommendation algorithm" or abbreviated "the algorithm") has a lot of political power to decide what you see and what you don't see, and that's frowned upon. Because everybody that has power over what you see and what you don't see is bad. That is why nobody wanted to provide an recommendation algorithm for the fediverse, because they would expose themselves to wild accusations. There should be an open-source recommendation algorithm, though; I'm sure of it.