"Along with a myriad of other inabilities and demons Lucas was tangling with, he never understood what made Star Wars77 connect with the audience. Like you pointed out, it was the simplicity. It was fun. It was an escape. It wasn't a government\economics course."
He understood that, he just didn't want to make the rest of the story simple fun. Defeating the Empire and rescuing princesses is more simple fun than the rise of an Empire and someone falling into evil. In reality, 4-6 are not just simple fun either when taken in broader context. He's on record that he knew the prequels would not be as populist as 4-6. It's not always about fun escapism and populism. This is the guy that brought us THX1138. He wants to warn individuals about society, not cater to society. He can't just pump out fun movies and do nothing else with Star Wars. The sequels weren't supposed to be as fun either.
"If the first trilogy is social and political and talks about how society evolves," Lucas says, "Star Wars is more about personal growth and self-realisation, and the third deal with moral and philosophical problems. In Star Wars, there is a very clear line drawn between good and evil. Eventually you have to face the fact that good and evil aren't that clear-cut and the real issue is trying to understand the difference. The sequel is about Jedi knighthood, justice, confrontation, and passing on what you have learned."
And let's face it, if Star Wars 1977 had special effects like Logan's Run, it would not have been a smash hit. The special effects sold it to the masses. Spectacle. Circus. Attractions. The special effects were a breakthrough sensation. That's why everyone went to see it. In 1983, it was fans of the story and also regular folks there to see the kind of spectacle only Lucas could bring at that time. Nothing else came close.