This is an excellent point!
Even now, to set up a blog is not really that easy and frictionless for a non-geek, “non-techy” person. Try setting up a flat file CMS like pico anywhere (for example, freecms.pro that offers you free space and easy access tools). I wasted an evening trying to fiddle with minor tweaks here and there needed to get the header look right, or the series of posts should flow like a nice blog. Or even deploying ghostblog somewhere.
In comparison, Medium is practical, aesthetic, free tool that builds an ecosystem for you as you focus on writing. Plus, your ideas spawn new ideas, they get a life of their own. Having said that, it’d also be wonderful to have the versatitlity of something like a jupyter notebook with the elegance and simplicity of Medium.