Mastodon actually lets you follow hashtags, which is a nice compromise, but it definitely isn’t curated so you gotta pick which hashtags you follow kinda carefully.
Yup. Tags are the solution, however it’s incomplete. It needs user-assignable weights. Otherwise all sorts of noise seeps through them.
Another solution or additional one is to do it the way Lemmy does it. In Lemmy every post is added to a community. The community serves roughly the function of a tag. E.g. /c/Linux -> #Linux. Then from all the topics in /c/Linux, users up/down vote to get what everyone following #Linux wants to the top. When I look at #Linux in such an environment (sorting as top) I get the stuff that others found useful, while the noise is hidden away. Organic sort based on user votes per tag or collection of tags if you will.