It's absolutely with the apple ethos of making you upgrade their crap when you don't want or need to. In this case if you have to upgrade AND they can cross sell you, up sell you product you don't want and then also sell access to you to third parties it's the apple living their dream. User experience, that's just bait, surely you've noticed that before now?

Security patches need to be entirely separate to performance degradation patches. You should be able to say no thankyou to your vendor gimping your product without them holding the "no security for you" gun to your head.

When you buy a device, security patches for that OS for 5 years should be a requirement for the device being fit for purpose.