As far as "Gun Game" goes this game is actually on the lower end of the spectrum. This is a far cry from Arma 2 or something with more realistic gun physics that require compensation and what not. Gun game has nothing to do with the strategy of this game. I will actually put forth that the metagame is what ruined it for most people. CCP came out saying you should focus on a specific set of skills or as players say I'm a "Dedicated X". This is where you find the bad players and generally also where most of the bogus complaints come from.

The Tactical and intelligent side of this game is actually more akin to strategy games then fps games. It's all about hard counters, x will destroy y or at least have a large advantage, problem is most people can only do y and never do x, but that is a metagame issue perpetuated by vets and CCP. As far as FPS skill goes, it has none of the bullet physics of a arma game pretty much all the weapons are hit scan and the ones that aren't (PLC, Flaylock, Mass Driver) have fallen out of favor. Forge guns are also not hit scan but it's a slight travel time. And unlike say an unreal tournament game you cannot compensate for the hit scan weapons via mobility because that too is pretty low. I would compare this game closest to Halo which is not a high skill oriented FPS in terms of gun game. Not to say its popularity and Microsoft didn't turn it into an Esport anyways. It's really about hard counters in this style of game which is where most of the wrong QQ comes from. Since many players spec to fulfill a specific role they often run into a build that is counter to their role and they feel cheated that they cannot compete with it, this has been a serious issue in the scout and logi community as their original roles as "Not point defense" led to complaining until they were made viable for "Point Defense" which led to the now current state of "Why do assault suits exist?"

Logis are support, this doesn't mean they can't kill, I can kill in a logi, but I'm not supposed to be as hardy or viable as an assault suit at it. Same goes for scouts except in a different way, they are the Ewar flankers, they should be able to kill as long as they don't get caught in a firing line however given you can make them fairly tanky while avoiding most scanners as well as cloaking this makes them extremely good at running around shotgunning or CRing everything in sight. This change was due to the fact that scouts complained for months that if they were spotted they were dead... but that was the point of a scout. Cloaks came in making surviving as a scout easier being able to maneuver for surprise flanks, however 1.8 also brought a boost in slots increasing their durability as a consequence. If you can survive open warfare why wouldn't someone just use a smaller and faster frame?

The reality was people had a choice when they started the game, either learn to be good with everything or pour everything into a specific tree of buffs to simulate being better at one thing. Most players chose the later which is why we have been in infinite buff-nerf cycle as players wrongfully claim foul because the game wasn't originally designed to be one class performs all. This is what FOTM is. The effort to find that one class which performs all which inevitably spawns from the poor design tweaks brought on by uninformed and biased complaints.

That said, although adv vehicles and type 2 were removed to "Get back to basics" the logi cars or as I liked to call them bumble bees were absurd. What made them absurd was that CCP gave them higher passive resistance then even tanks which made them extremely hard to destroy. Tack on the ability back then for LAVs to nudge kill any infantry and it became an unstoppable killing machine. I mention this as an example where some complaints were valid. Another would be 1.7 where a militia tank could shrug multiple av and it would take half the enemy team using av to neutralize one tank on the opposing side. That said, I stole a guys Madrugar with basic missles last night and with wise maneuvering devastated multiple of their tanks and infantry but if players bring out the big guns in Av I will die and should as hard counters are what balance this game. If there is no hard counter to a strategy then the game has failed from a competitive perspective. People often seem to forget that in the course of a battle you do not have to keep trying the same strategy. If you're dropship or tank got instantly vaporized switch to an infantry role and push the line with your team. If you are getting harassed by many vehicles then switch to AV and hope your team has the sense to do so as well. If the enemy has several Hmgs balled up on an objective with daisy chain logis use the arc weapons that do blast damage and REs. It's the stubbornness and inflexibility of players that lose battles more than anything. Pickett's Charge didn't work, yours won't either.

TL;DR: This game was never about gun game and teamwork it was about diversity of strategy and teamwork. Which the metagame crushed.