Im someone that does like the game, so not exactly who you asked for, but in my opinion its not popular relative to other fps' and lot of people dont stick with it because of either A) its pacing, or B) its barrier for entry/skill curve. Or probably both of these combined tbh.
I think initially the genre tag of FPS whilst true, can be misleasing for some that dont do the research before jumping into a game. Which isnt really anyones fault, its just the industry norm of fps games typically being faster paced and focused on well... shooting things. These things can occur squad but theres more involved/you have to work harder to get to them. You often spend as much to walking to a fight as you do actually fighting in squad. For someone like me, who has played a decent amount, it can still be frustrating to walk for 15 minutes and then die once you get to the fight. But I also know, that if I spend the time to communicate, plan and approach fights differently, once I get there and actually get to spend time fighting, its a lot more rewarding. For a player that is new, and doesnt know these things, they will likely only experience dying after a long run, maybe geting a few kills beforehand. At its fastest, squad is still pretty slow compared to apex, fortnite etc. Games like csgo are a better example of slower paced fps' having an audience, but even then, the scale is just not comparable. Trying to figure out what to do by communicating with 4 other teamates on a small map vs 40 - 50 other teamates on huge maps are two very different things.