I really don’t like the term “underrated” (or “overrated”) for that matter.
Calling something underrated without any context is not useful. What is it’s current rating? Are we assigning a numerical value for it? If it’s currently rated 8.1 but I think it’s an 8.2 is it still worth calling it out for being underrated? If we constantly call something underrated does it then become overrated?
I would prefer to just rate the film and keep it at that.
That being said, Return of the Jedi is my second favorite Star Wars film (behind the original) and is in my top ten films of all time.