As full on millennial I think I can add something to this.
I've had a social media account since the 6th grade, first Myspace and random forums, then Facebook then IG and Twitter. As long as I've cognitively placed importance on "social relationship" there's probably been a social network to build them on. In other words, a world with social media is really the only one I know.
It's impossible for me to compare to before my time, but I have watched as social has swelled to a level where it now just consumes itself. It's the sheer size and reach that I see as the problem. At some point it went from "let's connect with like minded people" to "let's connect with as many people as possible." What got lost was the value and community feel that was what made 12oz so dope.
I was definitely late to the peak 12oz community, probably 2007, but it still played a huge role in my graffiti and cultural up bringing. Interacting with and learning from people in partyinginportland, sketch threads, The Yard, Chanel Zero etc. felt like being part of an underground community. You can't get that on IG. It's to difficult to segment your audience on the platforms, so instead of passing through the grapevine it's shouted from the mountain tops. everyone is so eager to prove that they're in the know that keeping something lowkey has no value. Kind of ironic considering all the Privacy concerns people claim to have.
I'm not on Reddit all that much, but I have been able to find similar types of online communities on Twitter, mostly concerning sports. The problem there again is that you're shouting into a room full of other conversations and hoping someone hears you. It's less concentrated and in-depth for the most part, and character limits don't help.
The other major shift is the speed at which all of this is happening, made possible by improved internet, access, and devices. Having worked in digital publishing (including the 12oz Homepage) the rate at which content is consumed and turned over is incredible. It's made it difficult to have enough time to form real, thoughtfully constructed opinions on anything before the moment passes, meaning people are out here shooting off takes as they think of them. Sure there's more conversation and people talking, but it's less substantial. I'm reading Future Shock right now, and even though it was published in 1970 it's still incredibly prescient and relevant in talking about the rate of change and the temporary nature of modern life.
Can forums come back? Maybe... I know I feel fatigued and less and less interested in what is popping up on my feeds. Maybe a platform that's more focused and unique is the solution.