This requires integration of various systems, apps and services that just isn't possible until Apple really restructures the entire organisation and ways of working. Many things in Apple's first party ecosystem feel developed by teams completely unaware of other team's products.

There's two layers to this as well. The layer they handle reasonably well is integration between Apple products owned by the same person (less so shared products like Apple TV and HomePods), what they do terribly is dealing with the fact most people don't exclusively interact with people who exclusively use Apple products. God forbid, some of us might even use non-Apple products ourselves.

That means that you've got a bunch of really neat features built into the operating system which in practice you can only use one time it would be useful in twenty because the other people you want to use them with aren't using an iPhone. I'm thinking here of things like Airdrop only working between Apple devices, or the support for sharing audio from your phone/TV with someone else who's also got a pair of Bluetooth headphones only working if those headphones have an Apple logo on them.

Welcome to a large company. In my previous stint as an analyst, we'd be doing a consulting day with some group and a topic would come up and we'd be: "Um. You do know so-and-so in such-and-such a group is working on exactly this issue."