I think he was highly rated for three reasons, none of them very good:
-We had nothing else to grasp onto in some very dark times.
-Emery set up in a way that allowed him to get on the ball a lot.
-He had the passion merchant try-hard personality that was easily confused with a top mentality.
He was always terrible off the ball in terms of positioning, tactical nous, and other mental aspects of the game. But even on the ball it was more volume than quality. Once you see a player like Thomas Partey in the same kind of role its obvious that Guendog actually had very little in his locker in terms of range and diversity of passes, ability to make passing angles, receiving and turning in tight spaces, etc.