True, the analogy is probably broken. You certainly can ask Siri to play music from Spotify, I don't know who said you can't. That was added last October with

True, the analogy is probably broken. You certainly can ask Siri to play music from Spotify, I don't know who said you can't. That was added last October with iOS 13. I have no idea what's happened with Kindle, but I use Google Play and Kobo books as well as Apple's Books, and everything works fine for reading. If not being able to purchase books on the device bothers you so much, fair enough, it's your choice, but nothing much has stopped me from finding the cheapest source of an ebook in epub format and reading it.