He's lost a significant amount of pace, and even more acceleration. Same as Torres and Owen. They lose the confidence for explosive speed due to injury and they also lack the explosive speed for explosive speed.
We saw the absolute best out of him because he played in a team that perfectly played to his strength and Suarez's brilliance made him look better than he is. We then shifted to a playstyle that doesn't suit him, and is hurt by him, unless he's on form enough to draw more attention and score regularly. He can't get enough games to get back into form, not because of his manager, but because he can't play a run of games without injury. Couple all that with the fact that he's still a name and we have to answer questions about why he isn't automatically included, as if it isn't completely fucking obvious. He is more likely to get worse, bar the odd patch of goals, than get better, and he will never be part of our long term plans. Players like Origi, definitely his inferior in terms of skill, are right to play more than him.
We just have to hope that someone is stupid enough to pay over the odds for him. I would say they definitely will be. I don't see any reason to hate him though.