There is an open proposal to implement it without some of Bluesky's downsides.

https://github.com/mastodon/featured_collections

The main downside being the ability to opt out of starter packs (they can be a source of low quality interactions).

It's the opposite for me for one reason: hashtag follows!

There are very few people I want to follow for everything they have to say. I am interested in subjects, topics. Mastodon's hashtag follow feature gives me this. It's not perfect, you need to be on a relatively large instance to take full advantage of it (since it only picks up toots that make it to the instance) but it's still much, much better than no hashtag follow at all.

Personally I've always built my follow list via manual snowball sampling, so Mastodon discoverability is almost exactly the same as on twitter, except without the useless suggestions that I have to ignore at the start.

There's really only one trick to it, search for a hashtag and use the people there to get the list started, then it's the usually check at who's posting interesting stuff and who they in turn are reposting to find potential follows.

I have this impression too, I open Mastodon and the timeline usually doesn’t have many interesting things.

This used to be the case for me too, but hasn't now for years. I've followed plenty of people that migrated during the big exoduses from Twitter and then for a while started liberally following people whose reposts I liked and now the timeline is oozing with life ever since.

I don’t want to argue about the overall trend based on a single example, but Terence Tao’s substantial use of Mastodon for communication does change the picture a bit.

This is because you are holding it wrong. BlueSky and Twitter and alike are algorithmic attention grabbers. They try to feed you as much controversial stuff you might react to as possible. In the fediverse, there are no recommendation algorithms yet, so you need to make sure to connect with people you are interested in proactively.