I'm in a number of Facebook Groups, and they certainly have the element of convenience and the ability to instant message with the Facebook Messenger integration. We have the ability to customize our forums in a far greater way than someone managing a Facebook Group can though. We can really cater our sites to our audiences.
One of my forums is on mental health niche, and I believe it offers a good space for people interested in this niche, where people can talk without stigma or fear.
Social media is algorithmically manipulated. That means you see what the platform wants you to see based on your interests and activities. It constantly feeds you new and trending content to keep you on the platform in front of their ads.
It relies on viral content or content that is hot for a short amount of time and then moves on to the next.
I run a Facebook group with more than 50,000 members. It's huge. It's bigger than most big boards in the forum world. But there is no real community because so many things are going on and the algorithms are choosing what happens next.
On a forum, it's easy to login, see familiar faces and jump back into a discussion you were just having -- because there is no algorithm acting as the middleman.