Scoring? Yes, we have already established he was the best shooter. If it was only about taking, and making, shots, sure. Of, course it isn't. Steals? You have to be kidding. That is not a measure of good defense.
He was not better than Babb, and he could not play a lead guard like KL or the wing like Will. Great shooter off the bench though.
You have your opinion...many may disagree. Thomas starting this year is comparable to Mcgee's situation last year from this regard....many people felt Tyrus was one of the best players on that team. He wasn't coming off the bench because he was the 6th best player. Rather, he came off the bench because Hoiberg felt it most effective within the dynamic of the game. Similarly it doesn't matter if man 6 or 7 or 8 in the rotation is playing better than Matt Thomas. Fred has shown in the past that he likes that dynamic coming off the bench.
You asserted as fact (which is actually just an opinion) that Mcgee came off the bench because he was not the all around caliber player of KL, Babb or WC. Many think Mcgee was better, which correlates with Thomas continuing to start despite superior play by Naz and Monte.