This is wrong. The vast majority don't want their OS (whether it is phone, desktop, laptop, etc.) to suddenly change. They want stability. They have invested the time and effort to learn the UI and integrate it into their lives, change disrupts this and wastes their time.
If you force them into learning a new way to do things you have just reduced the friction of them switching to some other platform. And that's how you lose customers.
It's honestly not that different. Messaging is just as easy as before. Using Calendar is just as easy as before. All of the apps that aren't Apple's are the exact same and will be for the beginning of the official release. You underestimate people and their ability to adapt to change.
If you force them into learning a new way to do things you have just reduced the friction of them switching to some other platform. And that's how you lose customers.