The guy who currently runs Newbie Mixes has taken a step back, so they've been on hiatus for a couple of weeks. Keep an eye out, they should be starting again soon, possibly as early as this weekend.
You just happened along the competitive scene at a mildly inopportune time, as the top players are gearing up for playoffs and the offseason is approaching. Don't lose hope yet, as things will ramp up before too long. For now, continue to watch competitive games to see how things work in a 6v6 (or 9v9 if that's what you're interested in) environment, and keep on playing. Have you tried tf2lobby.com? It's not ideal by any means, but it's at least slightly more organized than a pub and sometimes you'll actually end up playing a decent game.
If you think you're ready for it (i.e. you have a solid grasp of the competitive TF2 metagame) you can also add up in #tf2mix on IRC. I believe there's a guide on how to do that around here somewhere. Let me get back to you on that.
Additionally, I know there are a couple of steam PUG groups left that offer lower level PUGs that don't require IRC to get into. PwrPugs is one group that has a similar skill level to tf2lobby and generally better communication. PwrPugs run almost every afternoon, depending on who's around to run them. You can join that group here: http://steamcommunity.com/groups/Pwrpugs . They send out announcements when PUGs are starting and all you have to do at that point is hop into the mumble server (provided at the steam group page).
If you want more help, feel free to add me http://steamcommunity.com/id/o_w_l/ and I'd be happy to answer your questions more directly.