I'll never understand how Discourse (the forum software) became so popular. Something about the UX it has makes it feel tedious to use. And yet, FOSS projects embrace it time and time again.
Maybe I'm a creature of habit, but I actually liked PHPbb / IPB / SMF back in the day. Those at least had a hierarchy and layout that didn't give me a horrendous headache.
A traditional forum is great for building a community, and in many ways predates how communities organized prior to social media. You can have a forum with dozens of categories and even multiple boards, with potentially hundreds of active members, and very little seems to slip through the cracks. It's easy to return to past conversations and navigate through them.
Things like Discourse, though, are something that feel poorly suited to community organizing. Everything feels crammed together and jammed into a single-page layout. These kinds of forums often feel like a dumping ground for community support tickets when FOSS projects adopt them.