Most people point to the Ewoks and RoTJ’s general muppet-fest tone as the film’s biggest problems. While I tend to agree, my biggest beefs with this movie are -
a) Leia being Luke’s sister does not make a lick of sense. Putting aside the obvious romantic undertones of ANH (from Luke’s perspective in particular) the fact is that Leia couldn’t have been the ‘other’. When Yoda declared “there is another” he’d just been imploring Luke to potentially sacrifice Leia who, at the time, happened to be a captive on Bespin. This also makes the backstory absurd. Apparently Luke was ‘hidden’ at Vader’s old homestead and allowed to retain the Skywalker name. Leia was ‘hidden’ in a high profile royal house. The whole thing is dumb.
b) Luke doesn’t actually save the galaxy. After all the build-up of the previous two films Luke merely makes it his mission to save Vader. The fact that the Emperor is killed in the event is a lucky consequence of Luke’s selfish religious/family mission. The idea of any kind of legend arising from this is ridiculous. Show me a single rebel at the Ewok celebration who would’ve been thrilled to hear that Vader had turned out to be a nice guy after all and that Luke had hidden under a stairwell to facilitate this turnaround while people were being slaughtered outside. Some legend.
What’s worse is that this makes a mockery of the Force and the Jedi. The first films imply that the Dark Side is something you’re tempted and corrupted by - in Vader’s case it would have been the promise of greater power at the cost of his soul/morality. RoTJ shows us that all you have to do is lose your temper to turn irreversibly evil. Not only that, apparently Jedi are completely useless in a conflict situation. If a twisted despot is annihilating your friends with a super-laser, you’re not permitted to act aggressively because that’s the Dark Side. This is completely stupid. By that logic Luke was a veritable Sith Lord when he blew up the first Death Star.
I don’t know if any of the Youtubers currently getting serious mileage out of trashing TLJ read these forums, but my challenge to them is to dare to put RoTJ under the same microscope they apply to TLJ.