My opinion:
The higher up you go in the tf2 competitive scene, the more socially stunted and toxic the players seem to become. I played high-level medic in Highlander but never excelled in 6s. During my experiences in invite/adv-level pugs on pugchamp, where I was often the least experienced and worst player, the environment was rarely supportive. In contrast to real-life activities like sports and clubs, where people tend to be more encouraging, the tf2 culture lacks this positivity. While you can always choose to be kind and supportive of mistakes, tf2 is the worst place for that in my experience.
In middle and high school, when I was struggling socially, tf2 seemed like a potential good place. Now that I've grown and developed, I have the confidence and insight to choose healthier activities and pastimes. It's no surprise to me that the scene isn't thriving and PUGs don't run often - it's simply not a welcoming or kind environment! It took my some time to realize it, but you really do catch more flies with honey than vinegar.