I hear you!
One of my articles was censored and taken offline. I never got the same traction after. So I agree with your shadow-banning theory. I stopped writing for about a year because life interrupted me. I started writing again two months ago. I get way less traction now. I released an article two days ago that I think is one of my best pieces, and I got 20 views on day one and only read by 10. I don't even know how that is possible. I have way more followers than before, and the article is published in a big publication.
I am sad to see you leave. You are one of my favorites, but you're right. It's hard to justify staying now. The guy in charge of Medium says it's our fault and it's a market reflection of our writing. I guess I have nothing left to offer here then, and I can't justify the time it takes to write these articles with so little in return, even with the encouraging words I get once in a while. I can write in my journal and get nearly the same results.
So, I guess I'm "write" behind you. I did sign up for your Substack newsletter.