You’re right about the forums. While they’re useful as smaller chat rooms separate from the “main ones” (for example, someone in a Discord server I know started a forum for fanart and discussion about a specific upcoming video game), they’re completely useless as a replacement for traditional forums.
Also, like you said, the search feature simply isn’t good enough to be able to efficiently search through all those forums. While Reddit’s (and probably Lemmy’s) search engine isn’t great either, it at least has the benefit of being indexed by other search engines.