For certain aspects, you are correct - instead of sending in 75 infantrymen to hold a ridge, you can send in a few tanks and mechanized infantry using fewer peo

For certain aspects, you are correct - instead of sending in 75 infantrymen to hold a ridge, you can send in a few tanks and mechanized infantry using fewer people. However, the somewhat perverse reality is that the logistics and support requirements of the two scenarios are equal if not higher for the latter. The more technology/mechanization, the more replacement parts, ground and support staff, fuel distribution, and so on are required. On top of that, many of the very "high-tech" aspects of modern warfare that replace people have very limited utility. High tech aircraft, drones, and cruise missles can be used for tactical strikes to disrupt enemy operations, but they can't be used to hold ground.