This sounds like you have the map screen Zoomed out in (declutter mode) which eliminates all secondary roads.I don't have unlimited data on my cell phone so using that is not an option. I ordered the navigation upgrade flash drive for my 2013 Volt. The upgrade leaves a lot to be desired. Still many roads not listed at all that have been in existence for decades. The for price I really expected a lot more. Will have to rely on my Garmin for any serious navigation.
I used the Non-updated Nav map while on a two week 5600 mile driving vacation. I didn't have any issues as long as the screen mileage scale was Zoomed In to the bottom ranges.
I was on some pretty remote roads out West. But you really had to zoom in close to get road labels.