Detection is really fucking dumb in this game. It's bad enough to warrant a full point loss on review scale. You can be performing completely low-profile actions like WALKING and still draw attention outside a restricted area with enemy gangs. Couple that with near instant detection after killing someone with a hidden blade also in low-profile. Unacceptable. I have no idea what they were thinking here.
You eventually get a perk that makes gangs ignore you in free roam.
You do get detected for BS reasons (this has always been a problem in AC games IMO), but it is much easier to go back incognito in this game compared to all the others. So at least there is that.