Gundogan was by no means average in his first four seasons at City. He was injured for the majority of the first, for one. But as others have mentioned, he was a fine squad player in the 17/18 season - his first proper season - and then covered for the #6 and #8 positions when De Bruyne and Fernandinho were injured for the run-in during the 18/19 season. He had a bit of a below-par season in 19/20 but, honestly, aside from Sterling and De Bruyne, so did everyone. From 20/21 he's been exceptional, but calling him average beforehand is a bit much imo.