Let me put this as simple as I can:
Writing tutorials on Medium means you are putting them behind a paywall, thus restricting learning opportunities.
Medium is not StackOverflow, it limits the number of articles that can be freely read.
If you ever learned something from a blog or from stackoverflow do contribute back by sharing your knowledge open on the internet not behind a paywall.
EDIT: For context, I don’t mind people monetizing their content, but in that case I’d rather pay them directly (like GoRails), and not a “subscription” for something I might check once in a while.