I think if he wants to get to the show he needs to dominate at this level and I will give him the cavaet that most of the Stars players are awful and it is hard to get your rhythm if you are surrounded by stiffs.
Fitts is averaging 18/6 with 2 steals and a block. He's shooting 48% from the field and 82% from the line. The problem is that he's shooting under 30% from 3pt (as is Butler so far). I don't think Fitts is going to dominate in the G-league. For one thing, the Stars run their plays for Butler and Hughes more than Fitts. As you mentioned, guys on the Stars aren't very good, and they can be pretty selfish as well. (For example, Alston is taking 12 shot attempts per game despite shooting 28% FG and 19% 3PT.)
The appeal of Fitts is that he's an NBA athlete, he's a good finisher on the break, and he can create for himself from mid-range as well as knock down 3s. He's also a good enough ball mover to fit in Quin's system. I could see him playing at the SF spot and fitting in.