Transportation technology stagnated since the '70. That's correct.
No, it's not. Not even close. Take a car from today and compare it to a car from the '70s. Other than having four wheels, a steering column, and an internal combustion engine, how are they alike? Car technology has changed dramatically over that period, particularly in terms of safety features and efficiency.
No, they don't fly, but then the market's not been looking for flying cars, either.