it's pretty obvious to me apple intentionally cripples their older products to coax people in buying the latest model.
think about it. if you update the OS and realize it's not good, you can never ever revert! why is that??? it's because you are now SOL and it's time to buy a newer model or....get an android.
on my android, i can install any ROMs from honey to lolli, or lolli back to honey. on windows, i can update to win 10 or go back to xp.
Remember the saying: never attribute to malice that which is adequately explained by stupidity.
It's nice to pretend that Apple is purposefully neutering old devices through iOS updates, especially if you're a diehard Android fan, but that just doesn't make sense. Besides the absurdity of the notion that it would devote lots of attention to making an OS
worse on old hardware (their hands are usually full enough adding new features), it's inconsistent with Apple's practices. Why would it go out of its way to support someone's 4-year-old iPhone, but in a willfully half-hearted fashion? If it really didn't care, it'd just drop support considerably sooner.
The likely reality is far more boring. Apple only has so many engineers, and may just have its hands full trying to support recent hardware, let alone something it hasn't sold at all for a year or two.
And repeat after me:
ROMs are not an option for most people. They're cop-outs to make up for vendors that intentionally abandon you quickly. And on Windows... no, sorry, that 10-to-XP example isn't true in many cases. Many PCs have hardware that just wouldn't work in XP (or Vista, or even 7) due to either a lack of drivers or just base-level OS support.
Besides, you're not exactly helping your case given that one of Microsoft's core problems is that tendency for people to either cling to old operating systems or revert back. Yeah, I'm sure Apple really wants a security mess where most users are running operating systems at least 6 years old.