I also tried it and yet I cannot follow the criticism of the UI. The one thing that is bad about mastodon is that it goes like: "cool, you wanna join? Here is a hundred choiced where to join and you better make the right one."

The interface is something I actually like better than the twitter one. I can actually see content from people I follow instead of weird "engaging" content. The website definitly is more usable than e.g. Instagram, which belongs to a multinational megacorp.

There is many clients but none of them seemed nightmarishly bad. The things the clients I tried offer work and are self explainatory.

The thing is: I tried mastodon years ago for a day and did also not grok it, but this had nothing to do with the UI, and everything with the people I followed and the instance I have been on. Then it is pretty much like twitter with multiple federates servers.