This is a straw man. What’s wrong with Medium being a publisher on its own platform? Instagram publishes content on its own platform, from its official main account, an official music account and probably some other accounts I haven’t noticed. Snapchat has its own in-app channel. Medium has its own publications hosted on Medium. So what? When you build a platform, it only makes sense to use it. Furthermore, you must use it. Why should you expect anyone else to use/experiment with it if you don’t?