A true freshman starting doesn't always mean that player is good. Look at Heaps as a frosh. We were desperate as we are now at the running back and tight end positions. Bushman and Ula are probably going to be great eventually, but neither are great yet. Jamaal was a 3 star according to rivals. He had a bunch of offers too.
You forgot Kafentzis is playing some QB too in mostly wildcat scenarios. We've had 2 healthy games of Mangum and 1 healthy game of Hoge and that's about it and the run game was never established in Mangum 2 healthy games. He was playing against long odds.
The Oline was clearly over matched this year in 3 games. Last year's line would have had the same result against those 3 teams. The Oline just isn't good enough right now to beat good teams. The running backs missed opportunities too, but what can you do with almost no push most of the time?
Defensively, there's generally enough talent to be better (except at safety and the interior of the Dline). Bronco's schemes probably would have helped with immediate success.
The bottom line is there is an experienced talent void right now. This team was never going anywhere whoever was coach. Maybe Bronco would have eeked out another win with this group, but the team wouldn't be dramatically better with this set of personnel.