Android Auto is far more than just a way to play music files located on your phone. Approved Android Auto apps (on a recent vintage Android SmartPhone) display directly on your Volt/Bolt center screen. Navigation is one of the main apps - you have a variant of Google maps and navigation appearing on your center screen. In fact, for the Bolt, that appears to be the only way you will be able to do navigation.
Now, the original post raises an issue that I have been concerned about, particularly with navigation on the Bolt. When you have to patch together all this crap from a bunch of sources, and it does not work, or works poorly, who is at fault? Who will fix it?
Is the problem with the cable, the phone manufacturer, the Android OS, the Android Auto App, your phone service provider, out-of-cell-tower-range issues, or something else?