99% is a horrible number to use there. The best team wins the Stanley Cup at best 20% of the time. If the best team won every season, Pittsburgh would have more championships, Vancouver would have won one, etc. It's a lot of situational happenstance on top of talent levels. Players get hurt, worse teams on good form beat better teams having a bad week, etc. Honestly, using the Stanley Cup as a be all measure of success is pretty out of whack. A team could win 82 straight games and then lost 4 out of 7. Does that mean the team is a failure? Maybe in the perspective of American sports. In European soccer, you can finish on top of the table and lose Champion's League and vice versa. Both are tremendous achievements and are treated as such. Here, no one cares that we were first in the East because we didn't win the postseason tournament.
Seasons upon seasons of mediocrity also doesn't apply. Mediocre teams don't win playoff series much less finish first in the East and make it to the ECF. That was 2 seasons ago with virtually the same roster.
This team is not nearly bad enough to warrant a complete rebuild when rebuilding does not guarantee you a Crosby, Ovechkin, etc. It's a smarter idea to continue to draft well and manage assets the best we can. We haven't been perfect but if you don't think we've been doing a better job building a squad the last few seasons than we did in the early 2000s, you aren't watching the same team.