As for the issue that the game is "broken" - it was for a while. It was fixed though. I wouldn't say it was broken now, just extremely, extremely difficult to get into. Simply put, it is impossible to casually play that game nowadays. You have people who play it day in, day out and have become extremely good at it. They know exactly where to camp, exactly what weapon to use, exactly what perks work, and when to use them. The game isn't broken so much as it's just overrun with fanatics who play it to the exclusion of everything else, and as a result, if you don't take it as seriously as they do, be prepared to get killed over and over and over and over again.
People say "it's unbalanced" because of Weapon X or Perk Y. Realize that you could use that Weapon or Perk if you thought it was so over-powered.
The reason I stopped playing MW2 was because I got bored with it. After I got to about level 50 or so, I stopped caring. I had got all the perks, and all that was left was a few more guns to unlock. After a while it became the same "spot dude, right click, left click, run, spot dude, right click, left click, run". As for "skill" it became an exercise in "who can spot who first, wins" or "who holds the best camping spot, wins". It was really fun for about a week or two, but after that.... it's the same thing, over and over. Some people can really get used to it, and will never get bored with it, and that's great!
Not the case with me, though. After you've played over 100 "team death match" games or "Capture the flag" games on the same maps after a while, you start just going through the motions.