Forums are pretty structured. Twitter and the new reddit are way less structured unless you’re talking about structured with ads built in. That aside, that’s a personal preference not a fact of the internet.
Yeah, when it comes to technical help a forum I found to be much more helpful, since relevant threads just don't die. When someone comments it gets bumped up increasing the visibility that some helpful person will see it and respond whereas on reddit/lemmy/kbin/etc types posts as a community gets bigger is pretty much dead and talking into the void after sometimes a couple of hours later. So that encourages having to post again leading to more reposting. It's just a much more quick rapid and temporary form of discussion. When you respond to someone those more modern takes on message boards the only one who'll see it is the person you responded to.
Forums by their nature don't need constant rapid activity of chats. Even on lemmy now as the activity has started to grow some posts are starting to reach the point that nobody will ever go back and read them as new content comes out. Compared to the beginnings where even week old posts people would comment on due to being visible. There's a place for both traditional forums and rapid modern post based message board experiences.