If you're using the Star Wars Prequels as some definitive statement of Lucas being a hack, then Peter Jackson is a hack since The Hobbit Trilogy is regarded as being garbage compared to Lord of the Rings.
The problem with the Prequels was Lucas being surrounded by yes men that wouldn’t tell him no. Lucas was heavily involved with The Clone Wars tv show, but had Dave Filoni with him to help, and it was an amazing series.
Well, that's what makes Lucas enough of "something" for me to casually substitute the word "hack" for that something.
You don't get to be credited as a genius, when you repeatedly demonstrate that you can only produce quality output with a host of others actively steering you. Even for the OT there are many tales of the others supporting him and shaping his ideas from their original form (as rough ideas that you and I could come up with in an afternoon) into the refined final product. For example, things as small as the fact that his wife is responsible for Chewbacca being what he is, and as large as Kasdan being an obvious reason Empire is what it is.
Nobody does it alone. A genius like, to pull a random one from my own idols, say Jim Henson would go out of his way make sure you were aware of the fact that he did not do it alone. (Meanwhile, I think Lucas would default to claiming he did it alone if he thought he could get away with it, which simply is never true and yet that betrays his 'hack'-ness even more...narcissism)... And yet, Henson stands as a genius and giant whose shoulders many have since stood on. So does Spielberg. Productions got better because he got involved (e.g. Gremlins, Poltergeist), or even when it was mostly him driving. Productions appear to get worse the less people are helping cover for Lucas.
I can't say the same thing about Abrams, he just is what he is. Nice guy, makes successful shows and films, but not much that really speaks to me or commands my highest praise (for whatever it's worth).
And Lucas, for that matter -- great ideas (some would question their originality but hey, like I said, nobody does it alone and that includes genesis of ideas), film icon, and all that ... but ... someone who seems over-rated.
I suppose, in general, that's really what I mean by "hack" if I should ever say it in conversation -- over-rated. Because you just know most of these people let it all get to their heads, and I don't like to see that happening if it's not well earned. And you're darn right Michael Bay is a hack. This discussion is obviously NOT about monetary value, it's about quality.