Man, people are just never happy. If Apple releases a more powerful, feature-packed operating system, which they support on their devices yeeeaaars longer than other phones, and it drains the battery, then it's malicious. If Apple slows down the phone so it doesn't kill the battery when more powerful operating systems are installed, then it's malicious. You have been able to replace the battery since the iPhone 3GS. I've been replacing my own parts for so long that all of my iPhones last me 3-5 years. Just because the design doesn't make it the most convenient device to repair doesn't mean you can't do it. They could've soldered the battery to the board if they wanted to. There are phones that have to be almost entirely disassembled to replace the screen, but iPhones start with the screen. The MacBooks are a whoooole other story, though, and are now the least repairable aside from the Microsoft Surface, so I'll never get one again. Apple does work against the right to repair legally-speaking, and abuse their users in some really fascinating ways which other companies do in their own ways, but a more powerful or throttled operating system isn't how.
