Lemmy posts are still designed to decay and fall off the front page. The posts last longer if they have participation but the only way to make something last a long time is to sticky the post so it doesn't decay.

Forums aren't like that. Forum threads are meant to stay around as long as people bump them and they can be ancient, with hundreds of pages of comments, and the thread still keeps getting bumped because new content is added to the thread.

Also, the way comments are organized is different. Our comments are threaded so we can have a conversation between us in a comment chain, but forum comments are sequential. The comments section of every thread would look way different if it was a forum.

Forums are just structurally different. If you don't like "link aggregator" that's understandable, it's actually not very descriptive, but you still need to be able to differentiate between forums and whatever-the-heck this space is.