Let’s not put those early phones into the same bracket with more modern ones — the phone market had a very steep improvement in its early years, that has only entered a more stagnating period a few years ago. Before that you pretty much had to buy a new phone each 3 years, now an iphone X is and will be available for many years to come.
That's just scaling difficulty. Android was pretty shit back then too and continued to have performance degredattion due to other reasons like storge implementation unti a few years ago - idk about now.
Not really relevant to modern iPhones, but they wouldn't know that if they've sworn off iPhones since.