eh - I would say the iPod is a perfect example of incremental design. There were other MP3 / digital audio players on the market before the iPod, and some were market successes, but they were clunky and had smaller storage capacity.This all sounds sensible (and boring). But once upon a time Apple DID innovate and "product design" was not simply incremental. Take the iPod as an example. There were 4/5 very different implementations -- the Shuffle, Mini/Nano, Touch and Classic -- with different features and very different price points. This is all lost when it come to the phone, every model is essentially "the same", with little tweaks here and there. There is no imagination, no variation, just a dull sameness ... all in the name of preserving Apple's 40% margins.
Apple did what it does best - see what the market was doing, and offer a product that was easier to use, with an attractive design (inspired in no small way by the work of Dieter Rams at Braun), AND that worked hand-in-hand with its iTunes music ripping/burning/management software which had been introduced earlier the same year.
Its genius was not in advertising its specs, but the benefit: "1,000 songs in your pocket." A way to bring your iTunes library with you, with automatic syncing.
The evolution of the iPod between 2001 and 2022 was very much incremental - refining the design to become thinner, smaller, more power-efficient, lighter as technology allowed, and as the cost of parts decreased, to introduce color screens, video playback, even a camera (in one iteration of the Nano).
Yes, the product line created interesting one-off branches, such as the square screen-only Nano, and the Shuffle which went from the 'stick of gum' form factor to its final clip-on version, but there's more similarity than difference when you look at the evolution between generations within a single version.
It absolutely was not like the design free-for-all of the early GMS cellphone market (hello, Nokia), nor the fashion-driven Japanese keitai phone market.
Arguably, the iPod still exists... it's just on your wrist now.