Honestly, most of the people in places like that are people who already found their way out, and now just want to shoot the shit with other people who understand what they’ve been through.

At least in my experience, that wasn't the case at all. I used to hang out in communities like that back in the late 2010s, and me as well as multiple folks were people who still hadn't managed to shake off their abusive narcissistic parents due to us being young teenagers or unable to get a job, and needed an emotional support group. While yes, there were also multiple people who already had shaken off their N-parents, they certainly weren't the only group and there were still many who either were still stuck living with them, or people who were living on their own but were still dependent on their parents in some way or otherwise forced to see them once in a while. And a nice chunk of the people who did manage to go low- or no-contact with their abusive parents still gave the emotional support for those of us who didn't have the means to do so.

Telling someone to seek professional help instead feels like such a slap in the face for people in such a situation because, for the most part, they literally can't - at best, it's simply because they're completely financially dependent on their parents and can't afford a therapist (and it might be resolvable if they get enough donations to afford checkups and their parents are the neglectful variety and don't really care about that), but at worst (and it's almost always at worst) they're control freaks who believe therapy is a scam and you wanting to do it instead of "praying the depression away" means you're not religious enough, or they would see it as an affront due to the implication of their child being traumatized by them and get furious and punish them, or be insulted/freaked out by them receiving money from strangers online and cut their entire access to the internet altogether. It's simply not an option. So having an online emotional support group they don't need to cough up money for is simply the next best bet for many, and while it won't solve the problem, it'll at least make it manageable. I know it did for me.