I'm gonna be cautious saying this because I don't have the full data that Medium has, but looking at my 2K+ followers, I reckon about 50% of them are readers only. I know it's anecdotal evidence, but still, the platform still veers towards democratised publishing (as intended about a decade ago) than community, which is fine and desirable, because if it ever becomes just a community of writers, then it won't be a sustainable business model.