And that's not because of the battery, that's just because of the software updates. Like, the CPU didn't lose any MHz along the way.
If Android doesn't follow the same path then I will be good-- if they do, then onto the next idea!
The software changed its requirements. Within reasonable limits that's just the nature of technological advancement and availability of faster hardware. I don't know if the performance degradation of iOS 11 and 10 were reasonable, but judging by user feedback Apple seems to have increased performance with iOS 12, particularly for older devices. Of course that comes too late for the iPhone 5C, which isn't supported anymore.
I don't want to hate on Apple. I have no allegiances to anyone in particular. I just am a cheapo user that values basic functionality, some speed, some longevity.
I don't put a premium on privacy or animojis or nice cameras or huge amounts of storage :)