It's not bad, I am having fun. If you like Crackdown than you will enjoy this. It just brings nothing new to the table and honestly I think it also doesn't need to.I find it hard to tell how much of this is Crackdown 3 being bad, and how much of it is the game having to bear the cross of a being a big exclusive game/being around so long.
From videos it basically looks like Saint Row 4 with better draw distance. (which makes sense really since SR4 was cribbing from Crackdown pretty hard)
The game just brings some heavy luggage because of the development and platform it is coming out on - that's why I think the reviews are what they are.