I mean, I havent really encountered any hacks or mods, just people with really good connection, and of course really good luck.
Whenever I am killed, most of the time it is either because my weapon cannot shoot that far, i was killed from behind, or i was simply headshotted. I mean of course sometimes i miss my mark, but that is how i am killed.
Sometimes, things just dont go right for you in a game, and yes it is the mechanics. But when things go right, it is because of the mechanics as well. Sometimes you miss people and sometimes people get very, very, VERY lucky with their kills. It has happened to me since i started playing CoD back in 08'. Most of the time it's either connection or luck. Sometimes it's because of the players skill.
I actually find this game very playable, although sometimes it can get pretty bad, but so can every video game.
Well let me add this I play COD black ops 2 and both have about the same amount of hours played, MW3 maybe a few more and my KD ratio and overall progress is definately better on Black Ops where mods are better controled. I see this daily on MW3 small caliber guns at majot distances with head shots constantly it's days are numbered unless developers start checking on it.