Probably because the only times Certain Affinity had some failures was when they made CoD Ghosts’ multiplayer and multiplayer DLCs, which didn’t result in a multiplayer that fans wanted since it was more teamwork based rather than “you all happen to be on the same team, just go ham” that Call of Duty is known for.
Other than that, their releases of DLC content packs and their works on making the core multiplayers of CoD World at War, Doom 2016, and Halo 2 Anniversary have been pretty successful and well made.
They literally have a satisfaction rate of easily 90% and up when it comes to their works.
I dunno what gripes people have had with Certain Affinity before other than CoD Ghosts.
Here is a link to show their current work history and upcoming work history :