Then you have two choices, disable iCloud photo backups or don’t upgrade to iOS 15. There are plenty of arguments against Apple’s scheme, but this isn’t one of them.
It's the best argument. Every other argument is based on a slippery slope what-if scenario.
Also, I pay for iCloud... but they're not paying me for using my phone and bandwidth. I never agreed to that.
They can't just pull the rug out from me after we already have an agreement. I mean they can, because I probably "agreed" to it and some fine print garbage EULA, but those fall apart in a court of law.
