I can't comment much about it as I have only played it for a short time. I spent about 3 hours in the Division 2 beta and roughly the same in Division 1 full game. I remember reading that a difference is in the dark zone but I haven't reached that (and don't intend to do PvP anyway). I do like the environmental setting though, there's so much details in the open world, the level/world design is just amazing.
From what I've played, indeed it feels very similar to the first game. The main reason I played so little of both is that I can't get into the core shooting and cover mechanics. When you are walking around the world, you will keep getting X prompts cos that's how you take cover. And when you want to more from cover to cover, you have to point the camera to the next cover then hold X. It's not a free motion thing. I understand that Tom Clancy games are supposed to be tactical, but I just don't like this. (Can't remember which other games did something like that, maybe Army of Two? Love that series though.) If they had implemented the normal shooter cover mechanics or no cover mechanics at all (the level designs will have to be changed if no cover, like having more pillars or such that you can hide behind rather than a flipped over table or something), I would certainly play this series. Something like Ghost Recon Wildlands (another Ubisoft openworld Tom Clancy game) cover system, or Uncharted, would be all it takes to draw me in.
The cover issue dosen't stop there. When you shoot from cover, normally games will have you pop up your head and shoot (I am not talking about blind fire here but proper aim and fire). In Division games, you will stand up and shoot, whole upper body is exposed from cover. What's the point of taking cover then? And when you reload (or sometimes it seem like the weapon jam or something and you are fiddling with it), you just stand there taking bullets from enemies. You have to release the aim trigger to drop back behind cover. Can't the game automatically do that? Instead of focusing on shooting, it becomes like a rhythm game where you have to remember when to release aim. And when an enemy comes next to you or behind you, you still can't just turn and shoot at them from behind cover, you will stand up and expose your back to every enemy while you take care of those next to you. And oh boy the close range shooting is just comical, from the enemy AI to the way you shoot face to face, it's terrible. (And melee, which the game doesn't teach you, only works a quarter of the time.)
Some of the button mappings are odd, like sometimes I just completely forget how to throw grenade (it's D-pad left). The game doesn't teach you about calling back your turret, but when I did that, it doesn't seem like cool down is shorten. There are a few other odd stuffs and bugs, like I have seen other players 'swimming' in mid air (they float while standing and the hands move around like swimming). Anyway, these are not major to me. It's just that the basic shooting/cover doesn't work for me and that's a showstopper. Of cos, mileage varies from player to player.