Here's the difference between CoD4 and Black Ops 2:
Call of Duty 4 -
Everyone had access to the UAV Killstreak, but by around level 15 or 20 you also had access to the UAV Jammer perk, which easily countered the UAV. It wasn't an issue.
Black Ops 2 -
UAV is a default Unlock. The only perk that counters it is Ghost, which is a max-level unlock, and only works while you're moving. The Counter-UAV is a mid-level unlock, and the stinger (or whatever it's called) keeps you spinning around in circles trying to find the UAV, all the while showing up as a red dot for anyone nearby to kill you.
So you can see where the difference is and where the complaints come from. In Black Ops 2, they went out of their way to make it so that a blind monkey can find people. This was because of all the complaints by people who played too much Pac-Man and got used to chasing down dots, they couldn't stand the fact that sometimes they actually had to look around to find someone.
So they took to Youtube and twitter and basically spammed Vahn for 2 years regarding the "overpowered ghost perk", completely exaggerated the problem, and eventually he caved to pressure and nerfed the perk into near uselessness and turning the game into "Call of Duty: Pac-Man Edition" where the goal is to just chase dots everywhere on the map.