CoD4 was the last good CoD.
CoD5 was made by Treyarch and was therefore doomed from the start (face it, IW CoD games have always been better than Treyarch ones - the only mould-breaker was Grey Matter's CoD:UO expansion) while CoD6 was the result of IW being pressured by a
complete and utter cunt to make a homogenised product across all platforms in order to use everyone's faith in the CoD franchise to rake in the cash rather than use the technology at their disposal to create the optimal player experience.
And as a final kick in the teeth, Activision then
fired Vince Zampella (the guy in charge of IW) for so-called insubordination! Way to thank your employees for their hard work, Bob.
The only probable reason Gamespot are saying this is because they're basing their views on the console version which, due to technological limitations (namely the makers not offering the console tech to third parties for the purpose of creating server boxes), has no other option than to use a matchmaking system.
That is all I have to say on the matter.