They used to have zero revenue and deep investor pockets. Now they have growing revenue and still have deep investor pockets. There's ways for them to disappear, but fewer than there used to be.
Re: distribution.
On a typical article, 80% of page views comes from within the Medium network through promotion by the Medium algorithm. Those page views (and even the followers of our publication) are readers that Medium sourced by publishing lots of other articles than ours. Their algorithm is much more reliable at driving 10k's or 100k's of readers than my other choices: mailing list, reddit, hackernews, SEO.
I’m not a fan of Medium (mainly because of the UI both on mobile and desktop) but it doesn’t seem like you have anything to back up what you are saying.
One question though - what do you mean by distribution?