That seems accurate in my experience.
I mean, not knocking who told you that at all, I think it's funny that they applied it to Medium the website. Just a little tidbit of info about the quote's origins, in case you weren't aware!
Usually you can find the signal in the first 2 or 3 sentences of in any post.
Medium.com has better SEO than SO and small personal blogs, so it's winning when searching for a solution.
Given the nature of the medium, books usually have the highest guarantee of quality due to the resources used to publish a book.
I won't try to guess why, but the few pages I can access are always high quality, while poor quality pages (as discovered when opening the page anyway in a full browser) always try to block that setup.
I suspect quality means different things to different people and even changes based on context for the same person.
For instance, a blog describing some arcane linux command to run to fix the issue you're having does not need to be the same level of quality as something you're reading to learn + get in depth info about a topic you know at a very shallow level.
At any rate, the idea is to somehow filter out all the garbage when I just want to know how to do something. Too often I have to find personal blog links on stackoverflow ("PS. I wrote more about it here") as opposed to that helpful article simply showing up in the search results by itself.
It would be interesting to see a curated version with an allowlist of domains as well, like how Angelfire and friends in the 90s used to be with a "web ring" of peer websites.
I have found several articles about Apache Kafka on Medium that have helped me a lot. I have no idea if it's by a junior dev or not.
I don't think they geniunely want to help people learn. I assume, given the low quality / effort content, that most are just trying to use them to build a prescence to help get jobs?
People see successful programmers giving lots of talks and writing lots of articles.
People want to be successful.
Monkey see, monkey do.