My iPhone 14 Pro is almost 4 years old and at 65% capacity. I don't know how everyone else is (not) using their phones.

I think you are the average case.

I follow the estimate that lipos lose 2-4% capacity per year without any use beyond recharging for safety. If the battery sees daily use that number gets a lot worse.

My guess is everyone else is the perfect mix of hardly any use and winning the battery lottery.

I’ve got a 14 Pro Max, used it extensively for four years and got mine at 81%.