I don't think I've ever looked at hashtags.
The point of Nostr is you follow people you want to read. Don't want spam? Don't follow spammy accounts.
Majority of new users first experience is an empty feed, a trending feed full of shit they have no interest in, a global feed full of automated spam reposts from twitter and every hashtag that should be useful to find people and content they're interested in following isn't until they've manually muted 100+ bots that spam those hashtags with telegram links.