@matthew
I still think there should be topic-based channels, but they should serve as a bottoms-up Schelling point for interests, kind of like reddit and content around them, that ideally no single person needs to organize (the point of an algorithm).
Once communities or products are actually formed, they should have their own identity and branding—not just the topic's, and the goal of those "branded channels" is to earn mindshare from the broader interest-based audience or group.
Might involve sponsorship or stewardship in many cases.