Reddit has been around for long enough that there isn't really a good reason as to why a user can't block out entire subreddits (vs "muting") from appearing in their feeds - there are ways to use the site that accomplish that, but it's not a very user-friendly design (imo)

For as long as I've been on Twitter it's always been super easy to block keywords, accounts, adjacently related topics, etc.

Anyway, I wholeheartedly agree with your underlying point that users should be allowed to curate their experience with a platform.