Lots of good stuff here although for this 74 year-old guy most of it went over my head. In a nutshell, the NY Times good news in luring people to pay for on line content may be an exception. I personally pay $1800 Canadian a year to have a daily delivered NY Times to my front door.
I learned about Medium quite a few years ago from the NY Times Business section and I immediately starting importing my daily Blogger blog into it. For a while Medium has installed a lovely import you blog tool that is a breeze. My only crticism (a very small one) is that I cannot seem to be able to get single spacing on imported poems! I agree with you Frederic that there is lots of banal stuff in Medium. But my eye immediately found your essay to which it is obvious you have put a lot of time to compose. There seem to be too many young ones in Medium trying to give us five of these or ten of those reasons why we should love or hate or buy. To me the most important factor in all of this is to keep writing without giving a hoot if anybody reads it or not. And I am not bitter nor do I rant about all that bad stuff.
I hope you are right and that Medium is able to bring in money and ads to keep going. As for me my Blogger blog (I hired a design firm to make it special and personal) is just fine.