Fitting a sufficiently large battery in the first place?
Apple have developed a chronic problem in recent years - stripping out engineering margins in the interests of aesthetics. Fraying MagSafe cables due to inadequate strain relief. "You're holding it wrong". Touch disease and bendgate. Stuck keys because of wafer-thin tolerances on the butterfly keyboard. Macbook CPU throttling due to a marginal thermal solution. Pitifully poor battery durability on EarPods. Display flex cable failures on the MBP.
The minimalist aesthetic has long been a key part of Apple's brand, but they are crossing the line from "minimalist" to "inadequate" with increasing frequency. It's working, for now, but it's eroding their reputation for quality. I've been recommending Macbooks to non-technical users since 2006; I can no longer do so in good conscience, because of the very high price of an entry-level machine and the high probability of a major failure.
Your second sentence contradicts your first.
Apple know that battery performance degrades over time. They knew that the batteries they were fitting to iPhones would be unable to supply sufficient current within the normal working life of the phone. They either didn't care about longevity, or chose to prioritise aesthetics. For a company that likes to brag about their environmental credentials and the quality of their devices, that's not a good look.
It's not voltage, it's discharge rate, which is directly proportional to capacity. All else being equal, bigger batteries can supply more current. It hasn't cropped up in the Android camp because Android phones use bigger batteries.
https://batteryuniversity.com/learn/article/what_is_the_c_ra...
Samsung was fined for exactly the same thing Apple was doing.
https://www.businessinsider.com/apple-samsung-5-million-fine...
https://www.theregister.co.uk/2018/10/24/apple_samsung_fined...
Thinking back, I remember how I basically had Stockholm syndrome with my phone. The performance was incredibly terrible. Swiping on the screen took two or three attempts, opening any app took 2 or 3 touches for it to register. Scrolling was stuttered in any app. I remember my partner deemed my phone unusable (it was 3+ years old, so I certainly expected some sluggishness). I had just built in muscle memory to use my phone, swipe swipe, press press press to open an app.
Sigh, and I'm still with Apple.
They were pretty clear that the battery throttling on phones with old batteries was to prevent the phone from shutting down under high load.
I'd argue that 95% (maybe higher?) of the public and the press don't understand this and still believe Apple was throttling the phone speed to force them to buy a new device. You even see this on HN a lot where people should know better. Bringing attention to it may just have caused the bad media response earlier.
They weren't clear that they were battery throttling on phones to prevent shut down.
Only to the fully rational. Many people would rather have their phone crash faster.
Also, any modern phone with bluetooth is just as capable off running airpods or any other wireless headphones whether or not it also has a 3.5mm jack.
Lastly, eliminating the 3.5mm jack has nothing to do with making the phone thinner either. My jackless iPhone 7 is actually a few mil thicker than my older yet nearly identical iPhone 6 which has a 3.5mm jack.