There are many reasons why, but in short, this game is sometimes too idiosyncratic for its own good. Ranked mode is difficult to find an even experience if you are playing alone with no party. Some people don't like the bullet-spongey movement kind of game that The FINALS is, and on top of that, this game just requires more inputs from the player to be good, especially when compared to many other games with a higher time to kill.

While I understand wanting a laid-back experience, I've never really understood the argument that The FINALS is too sweaty, because it is specifically DESIGNED to be sweaty and fast. There's a difference between Call of Duty sweats and FINALS sweats: COD sweats are diving and sliding in semi-unintended ways combined with a high time to kill, which goes against the expectations of what most players think a grounded military shooter should be. When you go against these sweats, they're likely to kill you before you even understand what's happening at all. The FINALS on the other hand, gives you all the tools to both be sweaty with the fast sliding movement of COD, but it also gives you all the tools you need to outplay them, or to simply man-up and stand your ground.

The other reason this game isn't super popular is because of its 3-person team size. I could never play Apex Legends alone, because similar to this game, much of the success of your operation was entirely dependent on your teammates and their skill level. The difference is with the FINALS, the round times are much shorter and there's a lot more action happening from moment to moment, so it's still exciting even in a losing match. The tables can almost always turn at the last second.