Stiverne is pretty good imo, he's just kinda lazy and looks to counter exclusively a lot. He can do that though, and he can move a bit, Wilder hasn't seen any of that.
If Wilder used his jab well and kept range to throw the right he'd win easy, but he didn't do that at all the other night and maybe isn't very good at it. If he comes in so sloppy again looking to fight I think Stiverne is well capable of taking him out.