Awful user experience can be anything from side-effects of decentralisation (no, you can’t search the entire Fediverse for something; no, you can’t even search all of Mastodon for something) to Mastodon’s official app being crap and people being unwilling/unable to use an app that isn’t named “Mastodon” to Mastodon refusing to catch up with the rest of the Fediverse in features to Mastodon refusing to finally become the 1:1 Twitter clone expect it to be. Mind you, the latter two contradict each other.