What significant improvement did Achille Gaggia's espresso machine offer over steam-based machines?

Achille Gaggia's espresso machine made a significant impact on the brewing process by introducing a method that utilized high pressure to extract coffee. This innovation allowed for the creation of a smoother taste with less bitterness compared to steam-based machines. The high-pressure extraction technique enabled the coffee oils and flavors to be released more effectively, producing a richer and more aromatic espresso. This direct flow of water through finely-ground coffee at a consistent pressure not only highlighted the desirable flavors but also minimized the extraction of undesirable compounds that contribute to bitterness. Thus, the result was a superior coffee experience that was less harsh, fundamentally changing how espresso was perceived and enjoyed.