Super interesting read thanks for posting Marxist. I totally agree on must of the points, and I'd say for sure leading a team or even just being a good teammate is definitely applicable to the real world. I think biggest game changer in terms of tf2 stuff for me at least was the praising accomplishments thing, because it can literally transform a toxic mumble atmosphere almost instantly and help hype up your teammates and get them all in the zone as well. Insisting that you know better than your teammates and bringing up arguments mid game 100% takes them out of the present moment and makes people play worse for sure.
I noticed a similar thing when learning about mindfulness, I found that a lot of the skills that are required to be a good competitor and receptive teammate go hand in hand with that stuff. Focusing on the game during a match and staying present no matter what crazy stuff happens and just letting it go is totally in the same vein as being present and letting go of your thoughts/emotions. Getting out of autopilot and focusing for long periods of time seems to me to be flexing the same sort of muscle as practicing mindfulness works on.
There are definitely a lot of shared skills, and I've even found that if I meditate for 45 minutes before scrims I actually play a lot better and am completely present and don't get tilted by stuff I would usually be frustrated by. Granted, it's also obviously important to play the game and practice mechanics and be warned up but honestly pugs can be so frustrating that it can just bring me into scrims in a horrible mood which is never something you want. I don't think people appreciate the significance of the mental game when talking about tf2, cause there's literally no way you're going to have any crazy comebacks or end of match clutches unless you're completely present and you aren't outcome dependent thinking about the possibility of losing and missing playoffs (I remember thinking this in S27 with velocity, I was ready to leave the sevrer after dropping uber and being pushed back to our own last and going down 4-0 but then I focused up and let go and we ended up miraculously coming back and winning). Patience is another thing that I actually found I had cultivated through playing tf2 (and medic in specific), being patient and waiting for the correct opportunity to arise and not pushing it and forcing something out of impatience is super important ofc.