This is the primary reason I stopped buying apple phones. I had to upgrade every 2 years due to the speed issue. I switched over to the note 2 and it ran like a champ for 8 years. I replaced the battery twice and it still ran very well before it finally croaked.
BS. . . iPhone don’t slow down due to battery issues. What Apple stated was about preventing older batteries "over drawing peak loads" which are rare events, not a common everyday thing. The actual thing a user in the past would experience, and WHY Apple added this capability to throttle the peak load draw, was the phone could just QUIT! No slow down, SHUT DOWN. Nice try. No banana.