Tags is a cool idea to help users find posts or communities on specific topics.
But taking away the different communities on the same topic is misunderstanding one of the key benefits of the fediverse over Reddit. I might want to talk about horses in a different way, with different people, operating under different rules, to the way others might want to talk about horses. The fediverse allows that, without having RealHorseTalk and RealRealHorseTalk nonsense.
Better UI and categorisation tools, yes. That'll help make sense of this for new users. But don't take away an actually positive aspect of the fediverse just to make it look more like Reddit.