See, from my perspective, a lot of teams in the league are wasting more than 5% of the cap, whether it's in dead space or overpaying players. It seems to be the nature of the system and it really doesn't much matter to me which one it is.
Just as an example, taken from a random team. Next season, the Minnesota Wild are paying Parise about $2.5m too much for his performance, Zuccarello $2m, Victor Rask $3m, and Devan Dubnyk $2.5m. They've got the equivalent of $10m in wasted cap space. OK, so you want to talk about a good team, rather than a mediocre team like the Wild. The Vegas Golden Knights are overpaying Stastny $2.5m, Fleury $2m (or more?), and have $0.5m going to Tatar in salary retention. Total of $5m in wasted space. Sure, the goal is to not waste any, but that's not really all that common of a situation. The Lightning are a good example of one at the moment.
My point is this: at this moment, the Rangers don't have a single overpaid contract extending into 21-22. Even with a Lundqvist buyout, the Rangers are actually in fantastic cap shape for 21-22. The only wasted cap space they'd have is that just over $4m in buyout dollars. And the year after? Even better. Obviously, barring any bad contracts between now and then.
Yes, next year is a problem. The Shattenkirk buyout does indeed suck, but this kind of thing happens pretty often to teams that are transitioning from one state of competitiveness to another. Signings that seemed well-advised when you're trying to compete no longer seem so when you're trying to build.