Original post is unclear.

I can figure out which lane of traffic on a given route is faster (which is something that Google Maps doesn't even attempt to do as far as I can tell). I agree that Maps/Waze can figure a better real-time route than I can, especially in unusual situations.

Both Google and Apple Maps are terrible at knowing when not to use local routes to theoretically save less than a minute or two of time.

In reality, you’re wasting brake pads and fuel in stop and go traffic that has far higher variance in travel time than a highway.

Google Maps has tried to route me through closed off bridges in the relatively recent past. I don't have a huge amount of confidence in the validity of its data.

It once asked me to drive my car along a bicycle path!

If you know an area well, you almost always can find at least slight improvements to the Google Maps route. When I know there's a closure or accident, I often look at Google Maps to figure out which way it's recommending and intentionally avoid that route.

How do you measure that your route was indeed faster?

Give you an example: A highway in my neighborhood is congested often but if you can put 3 people in your car, you are eligible to use the HOV lane and usually you can watch the cars next to you moving slowly while you can go in 50mph. Google won't know you are eligible for HOV lane and assume you are not.