I'd agree that aviation improvements have slowed way down, but they've certainly gotten dramatically better in that time frame.
And, while passenger airplanes do look similar to how they used to, we now have all sorts of drones flying around, some of which would have awed people in the 70s.
https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft#Histo...
I'd agree that aviation improvements have slowed way down, but they've certainly gotten dramatically better in that time frame.
And, while passenger airplanes do look similar to how they used to, we now have all sorts of drones flying around, some of which would have awed people in the 70s.