I think what ails this offense is when Heaps is playing is 99% mental, and not just with Heaps. If you work a job where you don't like your boss, you don't go out of your way to excel at your job. You don't go out of your way to develop a good working relationship with them.
Likewise in football, if players don't like the QB they're playing with, they aren't going to play well for them. They aren't going to go out of their way to try and make the grabs. They will just go through the motions. Then when they don't make the grabs it's easy to blame the QB they don't like. I believe this is part of what's happening.
The other part is (back to the job analogy) you have a manager who's cocky, thinks they're better than everyone else, and really doesn't do all that much to show why they have the job they do. They're resented by those beneath them, and co-workers will often try to undermine him in order to get someone in the position who they feel deserve it.
In football, you have a QB like Heaps, a great on paper QB, who has done little in game to prove he is the man. He's cocky and overconfident and takes some responsibility while excusing himself from other issues. He shows no signs of improving his game, and seems nonchalant abot the fact that he's playing poorly, deferring responsibility to other players (ie: run game, or receivers) The players take offense, and further, feel he doesn't deserve his position, and do little in exerting themselves on the field. They again just go through the motions while doing little to go above and beyond.
the problem at it's most basic, is that The players don't trust Heaps, and Heaps doesn't trust them. He probably sees it as impossible to improve when the teams plays hard when Riley is in, and doesn't when he's in. The team probably feels that as long as Heaps is playing that the offense is going to suck.
I'm not sure this ever gets fixed, because I'm not sure that the team will ever respect Heaps. Even if he sits the rest of the year, red shirts next, and comes back better than ever, there will be some people who only see the freshman when he's out there. They'll see the entitled, spoiled golden boy. I'm sad to say this, but I don't think that Heaps will ever have the respect of his team, regardless as to whether next time he's justified in earning it. as such, I don't think that he ever reaches his potential (There's that word again...). I think there will be too much bad blood.