This is a heartbreaking observation by Eric. He’s not anti-HTTPS by any stretch, but he is pointing out that caching servers become a thing of the past on a more secure web.
Can we do anything? For users of up-to-date browsers, yes: service workers create a “good” man in the middle that sidesteps the HTTPS problem, so far as I understand. So if you’re serving content over HTTPS, creating a service worker should be one of your top priorities right now, even if it’s just to do straightforward local caching and nothing fancier.