Well, it’s moreso that decentralization fundamentally means that there’s going to be a smaller audience for them to reach due to users being more spread out between instances in addition to the lack of ads and recommendation algorithms to spoonfeed their content to new viewers. Even if the UI/UX were more polished, IDK why they would prefer to use the Fediverse over significantly larger centralized services that basically cater to their use-case. The Fediverse is good for hobbyists and everyone else though, whom I happen to prefer for the most part.