In my understanding, George Lucas created the Star Wars universe and directed 6 episodes. Despite this monumental contribution, I frequently see various comments and answers on this site poking fun at George Lucas' ability.
A highly upvoted comment says: "It's because George Lucas is not good at continuity, or storytelling, or directing, or (this list goes on for a while)"
Various answers and comments mock George Lucas for being inept at writing dialogue
This answer basically says that the original Star Wars is great thanks to Lucas' co-writers, and that the prequels are so bad since Lucas wrote them
As a casual Star Wars fan I find this very puzzling. What exactly is the role of Lucas in the universe, e.g. conceptualization, directing, screenplay writing, guiding the novelization? (More opinion-based) How can the community seem to love the story yet ridicule the story-teller?
EDIT: Since some have expressed both interest in the question and the concern that it's too opinion-based, I've edited the question so that it is about an objective list of Lucas' contribution.