I don't buy into this whole "competent people are too busy for X". There's always time to socialize and mentor others. And even the best writers get writer's block for weeks.

I believe the main purpose for these groups is emotional support to becoming a professional. Which can often be in contrast to wanting to improve. So they can be very hostile to constructive criticism.

r/screenwriting is probably an exception. I think people who know about screenwriting are already very capable writers. More talk about how to solve specific work problems, or request career advice past 10 years. Less on trying to get your foot into the industry.

It's still no HN, closer to r/androiddev. In HN you have people talking about quitting FAANG. I believe in a top tier screenwriting group, you'll have more discussions on how to survive Hollywood, things like salaries at Disney, and such.