Brutal truth bomb. 100% spot on.

It's in Medium's interest to make their algorithm as effective as possible at gaining and keeping readers. If your stats take a nosedive, it means one thing: somebody else is playing this Medium writing game better than you.

The solution is clear: look at the articles that are performing well on Medium, and see if you can write something even better. If you can't, you're out of the game, go home.