I read his letter a little differently. I took it to mean Medium sponsored publications that use paid editors and push paid for content from outside writers. I didn't interpret it to mean the other publications that have proliferated on Medium for several years.
The Medium-created publications have pushed an agenda the entire time, which has probably alienated a lot of potential readers. Not so with the other publications. This might even be good for them, because they will no longer be bound by the strict guidelines Mediium has imposed on them for curation, which will allow for more creative and individualistic writing.