Let me clarify. If your post gets popular on medium, you may get lots of views. Views that won't necessarily translate back to traffic on your own linked custom domain and accumulating SEO credibility organically. Views from viewers who might never care about the source (you) and just care about the content fix of the day. By publishing on medium, you are in many ways an unpaid freelance writer. Yes, they offer a potentially far-reaching platform. However, it is a walled garden. The equivalent of people flipping channels looking for something interesting to read or repost in social media to burnish a certain image v. people who want to subscribe to what you write and link others to your content. The Internet is about niches. Take the time to slowly build your own niche v. being one of 500 channels on Medium.
Imagine if patio11 had started posting on medium (if it existed back then).