On the contrary, I'd want Cormier to be as fast and mobile as possible against Brock. Trying to match his strength is not a great idea unless you're Ubereem. Far better for DC to try and limit the up close engagements to as little as possible, darting in and out as need be.
Brock would love for DC to get in close with him. He might have the larger reach, but he's not planning on jabbing DC to death.
He completed dominated him, but I wouldn't say he himself looked great. I didn't see the speed he showed even earlier this very year, he didn't have the pop on his punches everyone says he carries at HW, etc. Lewis just looked so bad and uncoordinated in comparison that it was more than enough regardless.
Whether or not this is simply because of the short notice or whether it's because DC is slowing down is the question I started this thread for. I don't like how DC looked, and think it's a good idea he is planning on retiring against an older Brock.