There is a certain type of fan who seems to believe there is an orchard which has a Quarterback Tree, and when you need one, why you just go pick one off the limb. And this certain type of fan then feels free to excoriate management, coaches, anyone and everyone if that fresh-picked QB isn't "The One."
Your assessment is exactly correct, the Bills needed a QB and EJ was the best of the available bunch. And the Bills FO was very upfront about how he projected, clearly stating that he had a ton of talent but needed a ton of work. There was no intent to start him until the middle of the season at the very earliest, and probably not for a season or two. You know, the way it used to be done in the NFL.
So, a still-not-quite-ready QB was forced into action, with predictable results. What I'd ask the nay-sayers to do is to stop viewing EJ as a completed project who hasn't lived up to expectations and should thus be jettisoned. Instead think of him as a work in progress who, because of Kolb's injuries, is actually ahead of the projected learning curve. And for the upcoming season, look for a good bit of progress but still with much room for improvement. And if he regresses, the Bills can always go out to the orchard and pick another QB off the tree.