He's already showing he is something special, there's some people who are going to have to just accept they were wrong about him being all hype looks like he is going to be the real deal if he keeps this rate of progression up, it ain't just casuals giving him plaudits anymore.
Exactly the kind of step up he needed, evident from the first round he was several classes above him as a boxer(so it's not simply because he's built like a tank, some moan about the level of opposition but an Elite fighter wouldn't look any better against those fighters either because he's trounced them all, what more do you want?) also he's faster than Wilder and more powerful for me, after the Parker fight he'll be ready for him IMO... so he should chase that fight before Fury gets it.
My only criticism of him on tonight is it seems like he needs the other fighter to force something different out of him, like he is happy to just show us only as good as he needs to be for the opponent rather than how good he can really be when he pushes himself. The combo that opened Breazeale up came after Joshua got caught with something, Joshua immediately starts moving his head, moving his feet more and then let his hands go like he knows he would have to against better opposition. He could have done all of that several rounds earlier, could have gone to the body more, perhaps some upstairs downstairs combos to keep him guessing. Stick to the gameplan sure but in between the action when the opponent is giving you opportunities without being all that good on the counter he should have used it to try what else works for him, could have learned even more from this fight.