I don't think or recent PK woes are a personnel problem. I think the scheme is just bad/stale.
Yes I've openly despised the Avs' PK for decades now (I swear it feels like it's ALWAYS been shit, even when notable PK wizards like Ryan O'Reilly were on it) and even the new system they put in place is way, way too passive. Still does absolutely nothing to pressure puck carriers, box anyone out, or--most importantly--disrupt passing lanes. And as I've said before, making the defensemen hover around the goalposts instead of charging into the corners and along the boards like they should means the defensemen used HAVE to be very good skaters. Slow, lumbering types like EJ and Manson (and especially JMFJ) struggle mightily in this scheme. So not only is it a bad scheme, it forces Bednar and Pratt to rely even more on the top pairing. And it's clear Bednar would much rather use his third pairing guys, but he knows he can't.
And I'll die on this hill: Ryan Graves was a FAR better penalty killer when they sent him out there early on, he just went into the corners, knocked guys down, and cleared the puck. But at some point they told him, no, you have to stand there and block shots, and that completely ruined him.
So that said, they're obviously not gonna change the scheme now, so they needed to add more speed and hockey sense to the blueline. Walker IIRC has plenty of PK experience and not only has speed and skill, he plays with enough edge that I think he'll win the puck battles necessary to gain possession and clear it effectively.
Anyway, that post got away from me for a bit...nothing new there though.
tl;dr - Avs PK sucks, but Walker doesn't, and should fit the scheme much better than other depth defenders they have.