His skating is absolutely not great. It's a problem.
He's fine once he gets going but his footwork is bad. He's not very athletic and his agility is not good.
If you want to see why I think his offense won't translate feel free to look through my post history. Have been making that point for awhile now, just hope to god I'm wrong now that he's a Senator.
I'm not going to argue that his overall skating is elite but there are aspects of his game that benefit from his skating, his feet can keep up with his hands in various situations for example, driving down low for one, cutting to the net, he can straddle the blue line, he can work his feet in a way that get his shoulders square for his big, accurate shot. There are positives.
There aren't a lot of big defensemen that are 'ready made' great skaters that come out of jr. but there are a lot that develop that skill at a later stage to a very passable level. See Brent Burns as someone that Yak has been compared to.
Considering the base of talent he is working with and that his feet have good signs to build from I'm confident that skating will not be a perpetual concern with him.
Skating is a very fixable trait when lacking out of jr and it's almost expected to be sub par for a big guy like Yakemchuk. No concern here at all.