Better engineered sprayer jets, adding better sensors to determine water turbidity and other water metrics, additional sprayer arms (second-rack sprayer arms were pretty rare IME in the 90s, common today), automatic soap dispenser systems dispensing just the right amount of soap or rinse aid given on various water properties, etc.

Even today a super basic mechanical timer based washing machine probably won't work as well or as efficiently as a high end unit with various sensors and logic.