The thing is, mbin is right there if you want that kimd of functionality. There isn't really a reason why everything needs to evolve into omni-applications. It's better to have a broad ecosystem that has something for everyone, rather than a monopoly that's servibg everyone a compromise.
Just look at the Twitter mugrations in 2022, and the clammor for quote posts. Misskey was right there, giving them exactly what they wanted, but you couldn't speak the name of anything that wasn't "mastodon" because everyone is brand focused and context blind.
What OP wants exists. It's right there. It's just not named Lemmy.
Forums seem like the most natural use case for ActivityPub. I'm over the Reddit style UX, and absolutely ready to take a step back and try to pick an older jumping off point.