Rapidly reusable orbital launch vehicles were unheard-of until Falcon 9. The Space Shuttle was supposed to fill that role, but NASA, ULA, and government elements have made it a horrid overbuilt pile of feature creep that was, at the same time, the crowning achievement of American aeronautical engineering. The same thing that is currently happening to SLS.

Propulsive landing of a first stage booster was an insane idea. Even massive space nerds like Everyday Astronaut were skeptical, and I watched him cream his jeans live when the first booster landed. That alone, the ability to reuse both the structure and the engines of the booster, as opposed to ditching them in the ocean (or in China’s case, on top of villages), has made access to low Earth orbit significantly cheaper, and affordable to underfunded scientific organizations.