It is very hard to decide who th GOAT is between eras. I truly believe if you sent McDavid as he is now back in time to the 80's he would score 150 goals. Pretty easily. With the tiny crappy goalies he would just stickhandle the puck into the net. But what does that mean?
If you took Gretzky and moved him forward to now with modern training, diet, equipment etc I believe he would probably still be the Goat. But all era adjusted nonsense aside who really knows? All I know is I watched Gretzky's career live and to me he is still the Greatest because he was so much better than everyone else at the time. BUT, McDavid as an individual player is certainly more skilled, faster, stronger, better hands, shot, even passing, etc etc.