As a newcomer here, I've not the same historic experience nor perspective as others; I do, however, moderate on other forums (other subjects...), and there is constant evolution across all of these platforms. There is, in my view, a definite generational aspect; I recently retired from a long career in IT (and other activities...), so count myself among the 'old fogies' of this world. No, I don't naturally type acronyms such as 'lol', and have never grasped the sense of Facebook, Twitter, or whatever this week's trend dictates. Having seen all of the proudly-announced Operating Systems come and go, one becomes perhaps a tad cynical when a new gadget is brought out.
Forums..? In general (with many exceptions...), they are a fairly small core of regular members, with a flitting cloud of members signing up, to be never heard of again. This a fairly normal, I find, but those that stay are far more loyal and attached, and develop quite strong bonds between themselves. This, too, has its dangers when a new face appears on a well-established site, as one can easily get the impression of a 'clique' or 'in-crowd'. Welcoming new members is, I know, a thankless task, and the success rate of holding on to them is not high, usually, but when the magic operates, it's worth the effort, no..?
Are forums all the worse for social media..? Looking over a scale of decades, rather than weeks or months, I'd say that there's little to fear; those interested in hopping from App to Chat are often not the backbone of the forums (fora..?) anyway.
Now then; what about a nice cup of tea, eh..?