So the people that have good K/D ratios, that's all luck, right? They just happened to walk across people and just happened to pull the trigger faster?
CoD tends to be heavily twitch-based. But to say that it takes absolutely no skill to play is just silly. It takes still to APPLY your lightning reflexes. Hell, most of my kills aren't because of twitch. I know how to manipulate people into thinking I'm somewhere else, flanking them, adjusting my aim for the recoil of my gun, communicating successfully with teammates about where enemies are, where they are likely to be, and where they are likely moving. And knowing the map, that's also a skill. I know where people like to camp, specific chokepoints and how to approach them from different directions. Hell, even simply knowing when to shoot and when not to is a SKILL. Give away my position? Or perhaps move to a better position first, and then fire? Judgement has a lot to do whether you live or die in this game. Which path do I take? How long do I hold this point? Etc.
Time played adds greatly to all of these things. I played WaW first, and when I first started, I was absolutely horrible. Just really bad. I ended my career in that game with a 1.3 K/D, but I must have started with a 0.4, or something. Now, playing MW2, I maintain over a 2.0, easily. Because I've played the game a long time. The more you "practice" this game, the better you'll get. Pretty simple.
Oh, and map control is one of the most important things you can have in TDM. If you believe otherwise, you haven't played with a decent group of people. You don't truly understand what it is to dominate in this game until you get a group of friends that fucking OWN a map. It takes really good communication, and flawless teamwork, but my teammates have gone 7500-500 in TDM before. We've taken the time to go into private matches, and identify by name all the key landmarks on all maps, so when we die, or see something, everyone else knows immediately. But seriously, map control is very important. Holding key areas can win you games, as you'll restrict the movement the enemy can have to a few areas, which are easily watchable.