The fact that he's not 1st by a large margin in any category over the last 3 years kind of proves my point. Being a top 5 hitter and a top 10 pitcher for 3 years is extremely impressive, and shows a versatility we haven't seen since Babe Ruth, but being among the best isn't the same as being the best by a large margin, no matter how great the salary on the last year of his current contract is, or how good of a year he's having. When there's guys better than you, then you're not dominating on the field of play.
Over the last 7 years, McDavid has 126 more points than 2nd place, and the gap in PPG between McDavid and #2 is the same as between 2nd and 13th. He has the most ES points, most PP points, most GWGs and most OT Goals. There's only a few offensive categories over the last 7 years where he's not 1st, like goals where he's only 3rd, but almost everything he does sets the mark for everyone else to chase, year after year after year. That's domination on the field of play.