I recently discovered that you need to have Siri enabled for Apple CarPlay. I expect we're going to see a lot of this where when you disable the AI functionality the devs won't have put in fallback states and you'll be effectively locked out. With CarPlay for instance there is no reason that I shouldn't be able to listen to my music or use the map without Siri. But things like responding to texts does rely on Siri, s…
Apple considers siri essential for CarPlay and I don’t really disagree. Don’t forget that a big part of the design of CarPlay tries to explicitly discourage tactile use while driving, with siri as the alternative input/output method.
(I use Android Auto, but it's basically the same thing for these purposes)