My working theory to try understand the odd place he's in is that it's because he's possibly a bit culpable to the two things that frustrates fans more than anything. A missed sitter, and the odd dead end dribble. The dribble thing feels particularly unfair, as that's just part of his high risk, high reward game. I don't even agree with the over the top frustration re the missed sitters either, but I can see why it happens. I don't think there's anything that gets more annoyance out of football fans than a clear chance missed. The deflated groan is noisier for that more than anything. He can be a bit clumsy in front of goal, but it does feel OTT. I reckon there's more focus on it due to not having a striker, and people are taking their frustrations out on him.
Mad really, given he clearly brings so much. Football is so emotional though and people lose sight of past accomplishments and focus far too much on the tiny minor bits. As you said, he should be loved a whole lot more. Doesn't feel like he is by a lot. Shame. He's our best ever winger and a City legend.