Let's just bring out the most important aspect of this game, for any potential buyers.
1. This game involves repetition.
What I mean is you WILL do the same thing more than once. You WILL perform the same mission, over and over. You WILL walk around the same map, MULTIPLE times. You WILL encounter the SAME enemies more than once.
Basically, you will have many, many moments of repetition. The game is developed with this in mind.
If you are a person who needs constant change, new levels, scenery, enemies, boss battles, etc. to enjoy a game... stop reading now and go pick up something like Rise of the Tomb Raider (another amazing title), this one is not for you.
For those who enjoy the grind to the top, honing your skills, changing out equipment like weapons, gear, armor, yo help improve your odds on higher difficulty levels. You'll enjoy this.
If you enjoy playing with friends, matchmaking, pushing your skills to the limit with ridiculous odds in gun fights, this one's for you.
If the idea of a devastated New York, complete with underground subways, random enemy encounters, loot and gear to collect thorghout the city, sounds like a good time, you've found the right game.
If battling other players in areas that leave high level items for you to collect, while stressing about returning to a "Safe Zone" in order to actually "collect" your item, all the while staying alive in random gun fights... then you've found the right place.
The game is about becoming good at something you've done, over and over. Very similar to the game Destiny. And if you hated Destiny, save for the different location/characters, I can't imagine The Division changing your mind.
However, for those who enjoyed Destiny (even if for a short period) the new locations, guns, enemies and difficulty levels of The Division can keep you entertained for quite some time. Playing with friends or through matchmaking extends this much further.