a replacement battery.
In what world is this not a valid example of planned obsolescence?
Apple's only mistake was not proving the opportunity for people to choose from the start.
My iPhone 5 became slower after 1-2 years. If the battery was bad, I never noticed it (no shutdowns or anything like that). It coincided with a new iPhone and iOS version... I tried every trick, from formatting the phone to reducing animations. Then I found a thread on Apple forums about this and someone was suggesting getting a new phone!
I did buy a new phone (OnePlus One) and it's still working after ~5 years. The battery doesn't last as long, but it doesn't die when I receive a call or play a game.
Because of this, that iPhone 5 was my first and last iPhone.
So...it worked as expected? Slightly slowing the phone down is exactly what prevented your phone from potentially and unexpectedly shutting down.
Last year I upgraded from a mid-range phone which was almost 4 years old. It didn't have any "slow down" feature and it never shutdown, so as you can imagine, I'm not willing to give Apple a pass here.