>(Yes, there is an opt-in e2ee for iCloud now. No, nobody is using it because it is off by default and buried in settings.)
These are contradictory statements. It IS e2ee. I can easily convince friends and family to click through two menus to enable it. I can't easily convince my friends and family to go through the effort of installing syncthing on multiple devices and then go through with the configuration of them.
It's great you're a syncthing advocate, but telling people that icloud drive is bad just because they don't enable a setting that could cause an average user to lose all of their data if they lose the key is a little ridiculous. I GUARANTEE YOU that your grandmother would MUCH rather be able to call Apple to get her pictures of little johnny back when she forgets her password than have it "more secure by default".