No customizability. I want "continue watching" always at the top and have an easy way to remove shows from there. I never want to see "Watch it again" anywhere. I don't want any movies on the Index. And I want a clear sign which shows are dubbed. (Well, and I'd like Japanese shows to have English subs, but that's not a UI problem)
Over the years their interface got worse and worse that it's now at a point I need to use third party sites. So as they make discovery as hard as possible for me, I might as well cancel it whenever there isn't a release I want to watch.