I can only pick out a few flaws or missed opportunities, like Leia not getting the emotional reaction to finding out who her father is that Luke was allowed. I’ve never understood the hate for the film.
Yes, Luke’s plan to rescue Han is probably best enjoyed if you don’t think about it too much, but Return of the Jedi is like Revenge of the Sith in that they both have to spend the first third of the film taking care of a previously established situation (Han in carbonite, Dooku has to die at some point) and it’s my opinion that both do this in entertaining fashion.
Although I do sometimes wonder what the early concepts for the film might have been like on screen - Kashyyyk, ‘Imperial Centre’ etc. before they were channelled into Endor and DS2 - because it sounds like a film with more scope, I think ROTJ is a very dynamic and satisfying final chapter. I’m interested in hearing more of the issues people have with it because I’ve never been able to think of many.