I believe that the coaches would / should know better than any of us who the best QB on the roster is (don't take this as me being a JG sheep, because the the guy has been absolutely awful in both of the first two games and I would love to see Maurer and Shrout get plenty of snaps this week). With that being said, I think it is 100% fair to ask the question WHY do we not have anyone better to go with.
When Pruitt was hired, we still had a very real shot of keeping Adrian Martinez and/or Michael Penix on board in the 2018 recruiting class (if I'm not mistaken). Both ultimately signed elsewhere. Had the coaches succeeded in keeping either of those two on board (particularly Martinez), we have a different and better starting QB right now. Long story short, starting JG given the state of our QB room probably isn't the problem. Not already having somebody better than JG, on the other hand, is a problem that Pruitt is directly responsible for not having solved.