All you really need to do is deathmatch to be decent. Just have consistent aim and people won't complain.

However, if you really want to be helpful to your team 100% the utilization of utilty is a must. I went 2 seasons not knowing a single nade. I got myself out of a lot of shitty situations because of my aim. Now I'm not saying you're playing against good people on warlords(you're not) but if you learn to properly flash, etc you can kill your opossition without them firing a bullet in your direction.