In my own experience with things like this, the more "serious" players also tend to be more "defensive" when discussion comes up. Because our style of play is so much a reflection of who we are, some people will take any criticism of "how" as an attack at "who."
That makes it incredibly important to separate when you're talking about the players from when you're talking about the game. In fact, most problems come from different perceptions of that distinction.
When there's tension in a group, it's often because some of the more "serious" players place The Game at a higher priority than The Players. That manifests as frustration when a less-experienced player's mistakes "ruin" a session of gaming. Those inexperienced players are an obstacle, standing in the way of enjoying the Game.
On the other side, your less-serious players value the group more highly than the activity. Often that makes the activity itself an obstacle to enjoying the Group.
Addressing a problem is usually done by the Group-oriented rather than the Game-oriented, simply because of the nature of each. So basically, you're not setting out to fix a problem as much as you're finding out whether the problem wants to be fixed. So, some things for those Group-oriented folks among us to try:
1. A change of activity. Maybe a new game. Maybe a new way of engaging an old one. The #1 change that will clean up a lot of problems is to find experiences that are more cooperative than they are competitive. PvP content is the worst offender here, but difficult PvE content can be just as bad -- any environment that puts a lot of weight on each mistake is going to frustrate the Serious Players.
Outcome A: Group is receptive to it, and you mix things up a bit to find a good balance.
Outcome B: Group is not receptive to it, and you decide from there what to do.
2. A complete change of activity. Try "hanging out" with your serious friends while they play, while you play a different game at the same time. Talking here about teamspeak, etc. Separate activities, shared space. By removing the activity from the equation, you're just enjoying the company.
Outcome A: Group is receptive, and your interactions are mostly non-game conversation.
Outcome B: You discover that most of the conversation is "business," and non-game conversation is unwelcome or simply not happening.
3. Directly address the issue. Risky move, usually a last effort. Here's where you have a conversation about the issue directly. You're expressing how you feel about the current state, what you'd like to see, and how you can get there. And there are important things to remember at this stage:
- Focus on "I" statements. Don't accuse, blame, or target. You can only speak for yourself, so do that.
- Realize that while you have probably been mulling this over for days or weeks, and you have your whole case clearly thought out, they may well not. Sometimes, they'll feel completely blindsided. Give them time to think about their response, out of fairness.
- Listen to yourself. If you're tending to get angry, you may have already decided you'll be looking elsewhere -- avoid the temptation to use this exchange for parting shots (or burning bridges)
4. If nothing seems to work, it's time to move on. It's not a value judgment on either side, it's just a recognition that people move in different directions sometimes. Keep the door open on your way out, but be prepared for the 'other side' to react differently.
(EDIT: I've just recently gone through a "falling out" with a long-time group of friends over just such a thing. Some of these are things I wish I'd tried sooner.)