For writing longer-form than a tweet, with the social aspects (ie the possibility of getting people to read your writing), Medium has been great in theory (and is lovely to look at), but only so-so in execution. And with recent financial difficulties, it’s getting worse.
There are tons of free alternatives. I usually recommend Wordpress’s own hosted platform, which you can upgrade on if desired but most people don’t. There are weird and junky alternatives (I still don’t ‘get’ Tumblr), but some also-rans can still fit the bill - George R R Martin is probably the biggest blogger on Livejournal, for instance.