I disagree, for specialist forums. I am an active member on a couple of forums for woodworking, woodworking machinery, and antique/vintage metal and woodworking machinery. They are more active now than they've ever been, because the web in general has more content (manuals, tips, tricks) available for us to discuss (read: tear apart in a snarky shitty way, mostly).

For forums related to generic topics - business, politics, that sort of thing - then, yes, there are much better ways to get the information. But they were designed for consumption in the first place anyway. They were not designed for creation, modification, or real technical in-depth discussion.