I can give Lucas a bit of slack for the lucklusterness of the PT and ROTJ, since he was ultimately just trying to make pulpy Flash Gordon-esque adventures, not high-art movies. ANH and ESB, however, were so good that they’re generally considered to have entered into the realm of high art. He then fell into a trap where his subsequent films were expected to be masterpieces as well, and I agree that he could have definitely done better on them. But since he really knocked it out of the park on his first 2 SW films, fans’ expectations were higher than his.
I don’t think this opinion is too unpopular, especially around this forum. ESB especially came out amazingly good, but went over budget and probably gave Lucas ulcers from the stress. He probably never intended to make Star Wars that good - but it ended up being that good anyway due to “lightning in a bottle” factors like Kasdan’s script, Kershner’s direction, and the natural chemistry between Hamill, Fisher and Ford.