Same thing can be said why MGS fanboys complained why MGSV is open world and the new FOX engine and game mechanics. Same thing can also be said on Robocop, Batman killing people, etc.
People always have trouble adapting to a new theme or setting.
MGSV still needs improvement. It's about vengeance, and I barely have any feel of vengeance against Skull Face or XOF. Instead, I wanna kill Huey Emmerich.
Most of the main missions are destroy that, extract him, destroy some tanks, destroy walker gears, save that dude, etc. There also need much more contents to be discovered aside from fultoning random soldiers, materials, and finding diamonds.
Also, where the hell are the Mujahideen? >_< I'm doing missions in Afghanistan during the 1980s, and it's the Soviet-Afghan war. There should be random encounters, like Mujahideen fighters engaging Russian 40th Army soldiers or them taking down Mi-24 gunships with stinger missiles (Killer Bee in MGSV) or something.