The internet is for sharing. Social media is for driving engagement from users, mining their data, and encouraging unhealthy social comparison (as well as, you know, organizing events and messages and stuff). Nothing wrong with sharing a blog post on an experience you had that you think may be of value to others.
To dive a bit further into this, I was very socially active on the Internet 20 years ago, and it was a magical thing. I made friends that I still communicate with today, and I credit the amazing community I aligned myself with for helping me become the person I am today (in a good way).
Social media today is nothing like those early communities, and I rarely participate for that reason. Some of the core motivations (e.g. desire for connection/community) exist in both places, but the similarities pretty much end there.
The closest modern day equivalent (for me) is HN and some very niche subreddits.
Ditto. The important thing about the forums of yore were that they were largely composed of users who self-selected into it, and were oriented around a particular topic. They didn't have the thing were tons of people latched on and then just hung around for no reason other than their own boredom.
I think there's a fundamental difference in how forums are used vs social media. The catch-all nature of social media molds it into a device which people use to construct an idealized representation of themselves. Forums seem to head more in the direction of discussing/arguing about focused topics, rather than identity-creation.