Hill vs Siemian why is there a debate?

The dilusion that people have thinking Taysom Hill will ever be a quality starting QB in the NFL. He is basically the equivalent of a Ohio State QB making the jump to the NFL. They ball out in college but as soon as get into the NFL where defenses shut down their first read they panic. He is great in his current role as Weapon X. Why not role out with Siemian starting and Book backing up. If something happens to Siemian you finish the game with book and next week you turn TH into you starter.
Siemian is a professional backup QB, TH is essentially a rookie at this point. Just saying