I own an iPhone because I got sick of these kinds of issues I was having with my Pixel phones. (would last ~1yr of perfect bliss. Then the honeymoon ends and the phone would just behave like crap). I decided to give another brand a shot.
I'll tell you what will really tick me off in another year or so... If my device is, without warning, notification, ability to change, etc, purposefully nerfing itself for ANY REASON. That will make me really upset. Especially since I can't just pop the back off and toss a new battery in there.
Good faith or not. It's an anti-consumer move. If my battery even pretended to be removable, you might convince me otherwise. But gluing the battery in under a glued in screen and then throttling my device based on the battery's age... Just really bothers me.