Stanley cup winners typically play their stars (players & goalies) slightly less in the regular season. Whether this reduced load is because they have the depth, or because it's more conducive to winning the cup, or both, is debatable. Playing more in the regular season isn't worse from an individual standpoint, but it's not helping your team win the cup.
Some players (not necessarily the ones in the OP) tend to appear better than they are because they play a lot of minutes on a team that stacks lines and lets the rest of the team get caved in. So, these players will put up situationally inflated numbers and look unbelievable relative to the rest of the mediocre roster.
In the case of McDavid & Draisaitl, they probably won't make the playoffs without those two playing big minutes together. They also probably won't ever win a cup unless those two can each center a competent line. Baby steps, I guess.