Judging a player's career on whether he won a Stanley Cup or not is asinine. Winning a Cup is a team effort, it never ever hinges on on player, no matter how well he performs. It also gets increasingly harder to win one the more teams the league has. Needless to say, there is a difference whether about 1/6 of all players win a Cup every year, or about 1/32 of all players.
The only thing to judge a player by, are his individual performances. That includes whether he performed well in the playoffs. If a player delivers beyond what you can realistically expect yet his team doesn't win, that's nothing the player can do anything about.
Ray Bourque didn't magically become a better player just because he won a Cup on a stacked Colorado team. He was still a very good defenseman that year, but not remotely close to the player he was in 88, 90 or 91, when he didn't win the Cup. How come a good performance with a Cup-win is supposed to say more about a player than multiple amazing ones without a win?
Dominik Hasek won the Cup on a stacked Red Wings team. He wasn't as good as he was in prior runs. He had another great playoff run later on in which he didn't win, and then won another Cup were he lost his job as a starter. It would be weird to say the least to claim that this second Cup somehow enhanced Hasek's career when he was mostly warming the bench in the playoffs.
Jaromir Jagr won the Cup in his first two seasons, but never even reached the finals afterwards, even though he was a much better player in those years. Wayne Gretzky never won a Cup after leaving Edmonton, Edmonton did win one without him. The list goes on and on.
Winning a Cup or even Cups says nothing about a player's skill or career performance. Winning a Cup is about being at the right place at the right time. You can suck badly in the playoffs but still win the Cup. You can be a largely irrelevant bottom-liner who didn't do much and still win a Cup. Just like you can rip the league apart and not win the Cup. If one player delivers year after year up until a high age but never wins a Cup, and another player has a short peak before fading, staying on as a somewhat decent depth player, why exactly should the former be punished for not winning while the latter gets more acclaim due to riding the coat-tails of others?