No, people publish to Medium because it's very easy to do, and looks great. RSS doesn't solve the problem of having to create your own blog, host it, maintain it.
When your blog isn't your main job (or anything close to it), I really don't see the problem with using a service like Medium. We're all busy.
But is the audience for his post the same as the audience he's talking about in the post? I'd wager: no. Not only do developers tend to have more high-powered machines, this is a post we're much more likely to be reading on a desktop that a mobile device, compared to average. Plus, the post makes the point that a delay is hugely detrimental to any UI on a page, like buttons that won't do anything. Blog posts don't have that issue - you can start reading the article without JS having loaded yet.
The blog post repeatedly makes the point that you should measure everything you do and that you shouldn't apply blanket rules to your coding. I think the same logic applies here. The post being on Medium just isn't that relevant.
So we should only care when it's our job to, otherwise we're just too busy?
Even if one agrees with that attitude, which I don't, I'd argue it is the author's job to care.
Contributing to a bloated centralized service is not healthy for the Web. Making sure it remains a relevant platform is in his best interests, even from a purely egoistic point of view.
When your blog isn't your main job (or anything close to it), I really don't see the problem with using a service like Medium. We're all busy.