Lucas is bad at writing dialogue, by his own admission. Actors constantly complain about his directorial talent. His initial assemblies are notoriously bad*; he really has no idea how to order scenes or pace a movie, so the eventual quality of the film ends up dictated by his editor alone**. He doesn't self-reflect or criticize his own work early, unless he's prompted by people around him who are willing and able to push back. Lucas has admitted to pretty much all of this but blew it off, saying that audiences only care about sound and special effects anyway.
I thought the narrator was harsh, but otherwise 100% spot on. A lot of the things he said were real issues, and most of the big names in that video have publicly aired some of it. Essentially, though, Lucas is kinda bad at his job. He has poor incentives and doesn't want to improve; he's not dedicated to his craft. He's like the opposite of an artist.
Know where he really shone, though? He figured out that sad 30-something boomers would pay a ****load to see a 1960s high school nostalgia piece. He saw a new and obscure source of inspiration in Japanese films, especially their cartoons, and correctly predicted that it would resonate with consumers. He knew the real money was in toys. He has convinced people to buy multiple copies of 40 year old movies by 'tweaking' them just enough to generate controversy. (Did you really think it was about polish? lol.)
I mean, Lucas might be a perfectly nice guy. I don't know. But he ain't an artist, he's a businessman, through and through.
[sub]* Example: the ship infiltration sequence at the start of RotS was initially an entire hour longer, and introduced several new characters only to quickly kill them off. Most of the deleted scenes were Anakin and Obi-Wan killing CGI droids in CGI hallways while cracking the same dumb CGI jokes.
** ANH was rescued by Lucas's ex-wife, who not only provided massive input into the original script, but also edited the movie down into something watchable. Marcia Lucas was one of the only people in the world who has ever stood up against George Lucas and the result was magnificent.[/sub]