I believe NASA could also refurbish and re-use the SRBs, but the big orange tank was expended with every flight. The Space Shuttle Main Engines are actually still in service, we have a small inventory of them and they either have been or will be flown since 2011.

But I would definitely say that the moment the Falcon Heavy’s two booster stages returned to Cape Canaveral and made synchronized powered landings was the moment 21st century space flight arrived. SpaceX is head and shoulders above what anyone else is doing with reusable rockets and spacecraft. Meanwhile Boeing is in the broom closet huffing Lysol and muttering about quarterly earnings.