IDK the numbers they had but they could not have been that bad, especially with new content/seasons churning out. Like why did they stop on this game is baffling? Even if it did not meet numbers or whatever, you have this great base to build upon, change for the better, release some chunky content/raids/dungeons that brings people back. From memory it was always the loot that had the problems in this game.
Massive studios had a full team on Division like 5-6 years ago, then got shifted over to make the Avatar game, since that's done they've moved back to division and started making stuff again like the dlc last year, Resurgence the mobile game, another dlc this year, and div3. Red storm studios who were mostly responsible for the dark zone pvp side of the game also tried making another off shoot called heartlands which was a br/extraction shooter type of game, that got cancelled in 2024.
Loot problems were mostly solved after year one which went through 2-3 major changes to the stats and the random rolls, then the ny expansion added crafting to replace or maximize stats on gear (they already had this in division 1 it's like they ignored div1 when making div2) and expertise, they tried to add too much randomness to gear to stretch the grind for it in the first place, now you can replace one bad stat entirely, and maximize the low stats you want to keep, instead of looking for absolute perfectly rolled loot.
Seasonal play has been decent adding new story, new gear and exotics, new game modes like retaliation, the summit, descent, countdown(mega gear farm), and built up on different events in it to keep it interesting. While adding seasonal flavors, like this past season you could get a true sons npc ally to run around with you like a pet to help you out, or boost to certain areas of game play like one season skill builds might be really good, or the next one run and gun builds might be really good.
Division has a pretty loyal player base, ubi is lucky the game didn't die off like most other gaas games have.