First part of your post is quite weak.....
Does not explain the problem or explain anything
The last part is quite interesting and something which needs to be addressed.
COD maps are designed for defensive play styles in mind. Alot of lines of sights on one spot / area allowing somebody to move for each area and rank up the kills.
Something which has got worse as the series goes on..........
Camping a playstyle but when the maps allow a person to camp and do well you got a problem. I know alot of people are about to say "stop complaining about camping" , no it a problem.
It is a problem.....where the skill when i can camp a couple lines of sight and go 100-5 ?
It also kills aggressive playstyles or out smarting people when it comes down who has the line of sight.
It quite interesting that if you look at the maps some of them follow black ops style of design. 3 lanes of traffic and power positions which change based where people are. Other maps follow MW2 style of design of hard corners and head glitching. With not many power positions.
Some of the maps give alot of cover to the B flag on dom others not so much.
You sort of get the feeling........they wanted each map to play different to each other. Or that another dev team took over
MW3 runs off the COD4 engine. Just been changed over the years to suit MW3. Black ops also runs off the COD4 engine just again changed to suit black ops.
Engine alone is not enough to how a game feels.....other factors like how fast the player moves etc
MW3 has taken a couple steps forward and some back in terms of weapon balance. Almost all weapons can be used some are outclassed and weak as hell cough shotguns.
Taken step forwards with sound design i can hear people YAY........but then no counter to dead silence.
Backwards with the unlock system.........over black ops. Where i could pick whatever whenever. Also gone backwards on the spawns and netcode.
Just go back to the COD4 netcode patch the QOS so EU players don't get screwed and add in region lock problem solved. Or MW2 netcode.
IW and trey are two very different styles when it comes to game design.