Not every dman is going to be great at it but playoff teams have grit and toughness, Power is soft and casual. Good dmen have to have some level of intensity to their game, they have to be able to clear creases and get positioning (boxing out, etc). In juniors, we were taught first on puck, first on man, first in stick as the order of defending (Dale Hunter used to say that all the time).
Yes it's something you can develop (Hedman is a great example), no it's not something Power seems to be developing.
The danger too is that when you excuse and justify lackadaisical energy, it spreads. Teams follow the examples of their teammates whether that's matching intensity or gentleness.
Sabres have 3 great LD and a lot of holes throughout their lineup. Sabres are partially in their current bad vibes due to a culture that supports giving up. As much as they need warriors to fix that, they also need some good forwards especially at centre. 2 birds with one stone.