

It’s harder to see on a large Lemmy instance like LW, but most of the fediverse is very patchwork. The network of Lemmy sites is itself very patchwork, with the MLs, Hexbear, Beehaw, NSFW, etc. all having different defederation profiles, but the whole space is an incomplete mesh. Mastodon has more themed instances than Lemmy, more very small instances than Lemmy, and a much bigger anti-capital, anti-commerce bent than Lemmy, with many more people complaining on main about other instances rules and federation policies, so if you look, you can really see it.
But the whole fedi project is patchwork by nature.
Content aggregators are not forums. Just having categories doesn’t really cover it. CAs are designed so that old posts fall away quickly, so that people will keep posting new top level content and keep people emgaged in the constant scroll, much like Twitter or Facebook. They are largely unstructured, with different “categories” behaving quasi-independently from one another.
Forums are structured spaces where the same people post stuff to the same categories, that are mostly offshoots of the forum’s core theme.
People interact with and behave rather differently in these different contexts.