I have a 6, and for the longest time it would shut down at, 25, 30% battery. At some point (obviously when Apple implemented their fix) it “magically” stopped crashing, so I figured I didn’t have to replace my battery. However, I noticed it was dramatically slower - usually when that battery was low. I had a suspicion the two were related, but kept telling myself that was just crazy talk!
IMHO, when Apple originally added throttling, if they had just implemented a system setting to disable throttling for better performance, with a scary warning, and dropped the battery price at the same time, I’m guessing this would have been less explosive as an issue.
Problem is, that would open them up to questions on whether there is a design defect with the 6 series, bad PR, and (as always) class action lawsuits.
I think 2-year life expectancy on a battery is acceptable - but what I’ve never found acceptable is how difficult it is to replace the battery. I’ve swapped batteries in many iPhones over the years, it isn’t difficult for me but I always think of what a regular consumer must go through, and it bugs me. I really think this is the heart of the matter, as the battery is a consumable in a $600+ device, and is not easily replaced by most people.