I would agree if the purpose of GPS navigation was to allow you to drive with all your windows covered. It's not. When you're driving and can't see what's in front of you (because you're blinded by something, because there's fog, because it raining hard or because Batman is throwing smoke bombs) you have to slow down appropriately or stop entirely if necessary. I can understand following GPS indications and getting stuck in some mud but not falling of a bridge. If you don't see the rode in front of you: stop.

The expectation of safety should be on the local authorities. Clearly marking that the bridge is unsafe to drive over with signs and blocking off the area. While google should have marked it as an inaccessible route, it's the local authorities that should be looking out for the safety of drivers in that situation.