I have to take a moment to give him credit for one of my all time favorite moments with this team.
2016 - NYC host DC United. NYC is down 1-0 when Shelton comes off the bench. First, he harasses a DC player into a bad back pass that goes straight to Villa, who equalizes. Then, in the 85th minute, Shelton hustles to a ball on the end line and crosses it back to Lampard, who finishes. However, in stoppage time, DC United were able to equalize off a corner. But, a minute later, Shelton gets the ball on the wing, brings it forward, and slots a perfect pass to Lampard in the box, and he knocks home the winner. It was a thrilling game, and Shelton had a hand in all 3 goals.
I think it was those moments that ultimately made him so frustrating for people, because they showed how good he should be if he could develop any consistency.