Agree...I think Josh took time and progressed through all what you say very well.
When he was drafted, there were a ton of Question marks...but with a home-run hitting capability (Strong arm, fast legs, ability to move around and make plays)
His first year, several of those question marks regarding accuracy and anticipation were there as the Bills wobbled to a 6-10 record. But the kid showed heart and demonstrated that he would go to war...that was endearing to the fan. The Bills also realized that Allen needs weapons....they started stockpiling.
With offseason work on mechanics, Allen improved tremendously season-to-season. However, his play trailed off in the final month of the season with three losses. However, he played a great game against the Steelers to book a post-season berth. Accuracy improved, mistakes decreased....
Then he BLEW everyone in the next season....a season for the ages as the Bills hurtled into the AFC Championship game; Allen himself found that he was still not ready to compete with Mahomes at the big stage as he got his A** whooped....But he had exorcised the daemons on accuracy and anticipation...
The key was that Coach McDermott and Coach Daboll were patient with him and put him in the right opportunities. GM Beane surrounded Allen with talent that would help Allen become this better player.