My understanding is that search on the microblogging side of the fedi is intended to be "broken" (from the view of someone expecting a Twitter-style search); hashtags are for opting-in to global discoverability whilst without them your posts are intended to be stumbled upon and/or passed around rather than sought out.

Search is broken beyond the choice of being an opt-in. The fact that there's no way to sort search in any way except chronological order means it's hard to find anything relevant. Instead it's usually just a bunch of spam blogs or replies