There is seems to be lot of negativity against ranked ladders in the gaming community, but isn't that what would be best system to play with people of your own skill level.
I don't like playing a game where I need to worry about ranking systems. It adds a layer which I'm just not interested in. It's fine if I die more often than other people. Some of my fondest memories are of watching someone much more skilled than me absolutely steamroll my team. If you're playing with people you know, a vastly more skilled player becomes a fun challenge for you to try and overcome together.
For anything but 1-vs-1, individual skill gets smeared into the non-enemy (ally for team games, or everyone for a free-for-all) average.
Remember that cooperation isn't an individual skill (unless the meta is complete, I guess); it relies on knowing your specific partners.
And besides ... it's perfectly normal for a task-oriented group to have people at a variety of skill levels. If anything, homogeneity is what's strange. This does change what interesting interactions happen, but by no means prevents them.
It's a bit more nuanced than that, CS is a 5v5 game yes, but at low rank it's a lot more depedent on individual skills. I love community game servers but a lot of time those are for fooling around and not much the competitive skills.