I'm the type that prefers to look at a map to see where I'm going, and it drives me absolutely insane to have to pan up and down my route just to try to determine the name of a street I need to turn down.
For other use cases, I can somewhat empathize with the complexity of determining what street names to show. And over-cluttering with street names wouldn't be much better. But for a navigation route, the logic should be dead simple: throw a street name within the viewport if that street is part of the route.
(Yes, I fully realize I can switch to step by step directions. Maybe it's because I'm more of a visual person, or maybe I'm just old and used to using maps for directions, but I just can't stand using that view to figure out where I need to go.)
To add another nitpick, I often want to see the name of the street I’m standing on, especially in San Francisco which doesn’t like spending money on street signs it seems. But GMaps usually requires zooming way out or panning a non-trivial distance to find that. All the other nearby streets on the map have clearly visible names without having to do that, just not the one I’m one. It happens regularly enough to be annoying.