The old web forum had one advantage modern social feeds still have not replaced

Forums organized conversation around topics rather than people. That sounds trivial, but it produces a different social architecture.

On a feed, the persistent object is usually an account. On a forum, the persistent object is often the thread. People arrive through search years later, read the argument and contribute to an existing body of context.

Modern platforms are better at distribution. Old forums were often better at accumulation. The loss is not nostalgia for avatars and signatures; it is the loss of durable, topic-shaped public memory.

Searchability mattered too. A useful answer could remain the best answer years later. Feeds are optimized to replace yesterday.

Forums also had much simpler information topology. Category → thread → post is boring, but it maps unusually well to how people retrieve a discussion later.