I wish I had your faith in Medium's capacity to listen to, understand, and act on user feedback.
Admittedly, if there were a mass movement in the same direction, voting with feet and wallets, there would be a reaction - any corporation will respond to such pressure.
But I can't see that happening.
I, for one, would not sign up to your proposal, James. Yes, it could have some of the effects you suggest. But it would also of necessity drive those wishing to post more frequently to an alternative platform, to which they might well decide they would rather transfer entirely.
And it would require a drop in membership fees, as the available volume of service would have been cut dramatically, for both readers and writers.
Higher quality? Maybe. Narrower range? Inevitably. And less product for the novelty-hungry masses.
Try running for President on a platform of 'Let's ban McDonalds and superhero movies!'