The annoying part is that UX design for these use cases is well known. It's old boring stuff but Tesla (and other OEMs, but none of them have as much of a need for good touchscreen UX as Tesla) just won't implement it for whatever reason.
My guess is that they UIs like this just don't have the "wow factor" that will appeal to new car buyers.
When it comes to any user experience dealing with a touch-screen in a vehicle, I don't want to wow myself into the hospital. I love my TM3 but the UI could use some tweaking and I wished we had the ability to alter it.
Agreed, I'd be quite happy if there was an option to simplify the UI.