I am not against automatic transmissions since I drive a 7 speed, C7 Z51 Corvette Stingray. However cars with 9 speed slush boxes get better fuel economy since engine revs are lower.
That’s all in the vehicle/system design, not in the component selection.
At equivalent engine rpms, a m/t in a direct input shaft to output shaft mechanical connection is more efficient.
Do the manufacturers do that? Not so much these days.
More money to be made manufacturing and selling a/ts.