Not allowing downgrades is the biggest contributor to smartphones becoming e-waste.

Apple should be forced to do this by law, but only after they discontinue software support. If they're willing to continue making small, incremental patches when necessary (such as to fix this obvious bug) then it's fine that they can still block downgrades. But at EOL? They should be legally required to allow old software to be installed.

This also impacts software compatibility - any 64-bit device that is now EOL that got updated to iOS 11 or newer is forever barred from running 32-bit apps just because people are worried that someone might take that old device and downgrade it as an attack?

The average person should always stay updated to the latest version for security reasons. But the power users should be able to choose which version they run, at least on devices that aren't currently supported at all.

Daily reminder that the first two iPhones and the first iPod touch had zero firmware signing, and you could freely install any supported version at any time, and can still do so today. That being the case has probably harmed 0.00001% of people at most