It wouldn’t make him a better player, but he wouldn’t be worse. The major difference is that he would be “greater”. He would be seen as a winner and would probably be closer to Crosby on the all-time list too, if not ahead. McDavid will never be seen amongst the greatest (top 5) if he doesn’t win. It’s a precedent that has been set more than 100 years ago. It’s not going to change. I fully expect him to win one at some point, but he’ll never be seen as being greater than Crosby (who won a lot), if he doesn’t end up winning. It doesn’t matter how many individual trophies he wins, if he can’t get the big one, it’s going to be one big red flag in his resume. Like it or not, that’s how it’s going to be.
Bourque and Hasek got punished for not winning in their prime, with Boston and Buffalo respectively. They both have extremely good individual cases for the #5 spot, but instead, they were both seen outside the top 10 in the most recent consensus ranking on here. (Bourque was 10th, but will undeniably be surpassed by Crosby as the list was made in 2018). Also, I don’t even think there was a player who didn’t win the cup in the top 50, so that says a lot.
All the McDavid stans/Crosby haters can hope for is that the Oilers get more lucky in the next couple of seasons, because so far, McDavid has not been dominant enough vs his peers to be ranked above Crosby without winning the big one.