Not GP but I have some opinions as well. I would've been a Medium advocate several years ago. But all the things they've done in the past few years have been hostile to writers.
1. Got rid of custom domains, so you have to use a medium.com one. So if you're hoping to start a blog using Medium as a platform/engine but with your own domain, this is a dealbreaker.
2. Even if you have hundreds of followers, publishing an article on Medium does nothing about surfacing it to any of these followers. Your best bet to distribute the article is still posting on HN and Reddit or Twitter/FB.
3. On a related note, if you're hoping Medium would bring you traffic, it's 100% up to their editorial if they would feature your post on their homepage, email, etc. Probably best not to bet on it.
4. Various UI and UX issues pile up over the years. When you open a Medium article on a mobile on a fresh browser nowadays, you're likely faced with enough popups that cover more than half the screen. It's just not nice.
5. Most people hate their paywall. I don't have a strong opinion here myself.
TBH, most of the draw near the beginning of Medium was how easy it was to start an account and just write stuff, and the writing interface is nice. There has been a number of open source JS projects since then to emulate the Medium editor. IMO there really isn't any reason for anyone new to start on Medium anymore.