The Infotainment system is one of the most user-facing components of the vehicle. It's something that can reflect the brand identity of the vehicle, and most OEMs are not eager to cede that space to Apple or Google. Google and (especially) Apple certainly aren't interested in mixing their branding with a manufacturers.
The utilization of AGL doesn't necessarily mean CarPlay or Android Auto are out. AGL is a system, and CP/AA are applications.
While I certainly believe there are a lot of terrible systems out there, I also think there are a lot of systems that people don't like because they never took the time to figure out how to use them. Cars aren't like phones. When you're in them, you're most likely driving and you don't have the bandwidth to figure out how to do something as well as drive. A while back I saw a study that concluded if you didn't learn something about your infotainment system in the first 3 days, you never do.
I encourage you to actually identify the things you find confusing/frustrating/difficult about your vehicle and write a letter to the manufacturer. Customer input makes a big difference. And no, "It's not CarPlay" doesn't help. That's kind of like sitting down to Windows and complaining to Microsoft that they didn't give you macOS.
(Thoughts are my own, of course)