Maps not preferring interstate highways

I have a car equipped with autopilot in highways and it works best in interstates. In state route, however, I have to manually drive my car and I hate manual driving when I can autopilot.

The problem is that Maps does not allow me to prefer interstates highways. even with the “avoid highways” preference off, Maps is still preferring state route more than interstate route. It does not allow “drag to edit” my route either so I cannot plan ahead.

Therefore, I wish Maps has a preference to prefer interstates. And I don’t simply care about extra tolls or gas price incurred.