Apple only operate on an annual release schedule because their audience is not in sync. Most people keep their phones for 3-4 years but unlike games consoles this is not the same 3-4 years. New features steamroll so that going from a 12 to a 16 is actually a big deal.

If they reduced the frequency of these updates they would bleed customers. People coming into their next upgrade might be more tempted by a newer-looking Android device than a 2-year-old iPhone.

If the entire industry was like PlayStation or Tesla then this would not happen. Your ideas about reducing the frequency are laudable in an ideal world that we sadly do not live in.