Popups are quite intrusive. For instance, while Waze is recalculating, which can take a while sometimes, I need to see the map to figure out the next turn quickly. There are many other examples of intrusive popups, i.e. Danger ahead, Speed camera ahead, etc.

Popups should be shown as banners. A banner should be a rectangle less than an inch tall and as wide as the screen, aligned to the top or bottom of the screen. So, the rest of the screen would not be hidden at all, but would be instead completely available and usable as always.