I think people who claim that the UI/UX is fine are missing the point. It is fine to you, but it is not fine to whomever made the claim. And for every person that makes such claim, there are hundreds/thousands who think/feel the same but don't say anything.
Lemmy, as a community and as a project, should seriously listen more to the opinion of newcomers.
What are you supposed to do about the opinion of newcomers whose opinion is, "I don't like choice," and the central feature of federated platforms is choice?
Unexplained choices are extremely frustrating and cause confusion. It would be awesome if people could magically choose the right instance for themselves without being aware that they are making a choice, but that just isn't realistic.
Choosing was the only thing that was difficult about joining Lemmy, and it was difficult because I did understand federation and also understood that the feed and moderation would differ from instance to instance.
Honestly the only thing I can think of to make the experience better would be having the ability to preview the feeds from different instances with your settings applied and an easy way to move account settings to a new instance.
Easily switching is the real hurdle, because there are a massive number of reasons that someone would want to switch. For example I started on kbin and switched when the instance died.