Literally the only bad thing about the prequels is some of the dialogue.

Midi-chlorians, Jar-Jar Binks, the Jedi just accepting an entire army they had never heard of because some randos said they ordered it...

Lucas collaborated with a lot of people on the original trilogy. For example, he showed a rough cut of Star Wars to Spielburg and his friends which resulted in significant cuts and re-ordering of scenes. Empire Strikes Back, widely regarded as the best of the series, was neither written nor directed by Lucas

Lucas let his reputation get to his head on the prequels and both wrote and directed them himself. They showcase his weakness as both a writer and director. There's nothing wrong the story concept of a forbidden love affair corrupting a hero, but the execution is a mess.

At the end of the day, younger people are more generous towards the prequels because that was the Star Wars of their youth and they've never known Star Wars without those films existing. For those that are older, they're definitely a case of the whole being less than the sum of its parts.