I could go on and on about those features on that page that are there for ages, but one struck me hard in the last hour:
I tried cancelling my subscription, and after clicking on 6 "I'm sure" buttons and writing a reason why, I couldn't cancel because I was using too much storage (3GB, free accounts have a 500MB limit). I deleted everything on my Drive and emptied the trash, tried again, no success. Deleted all my emails and emptied the trash, still failed. Deleted everything on Calendar and Pass, nothing. Couldn't find anywhere how to contact support. There's a small bar that shows how much storage I'm using, one would expect that clicking on it would show a summary of what's using your storage, but all it does is show a popup with Proton's subscription plans.

I can't cancel my subscription because they don't have the basic functionality of a storage usage summary.