Recall the story with Medium - yes, you get broader reach with less effort, but at the cost of giving up control of your content.
I know that I am talking with an overly developer-focused lens (a-la "you can reimplement Dropbox in a weekend"), but self-hosting blogs outside the "walled gardens" is not super complicated even for non-power users. Ghost has existed for years and is a very user-friendly experience. Want to be a bit more technical - go the static site route.
It might be a lost battle to convince the majority of the social media audience of this (after all, can't beat the convenience and the cost of $0), but I really do not see this as beneficial to those that deeply care about their long-form writing accessibility and sustainability.
Twitter already has login walls to just read tweets, so I'd imagine the same is likely to apply to long-form content as well.