They are inventing a little, but the basics of rocket flight are now well understood. You can get a university (probably post grad) course on it. And nothing that they are doing is all that revolutionary, definitely not compared to what Apollo did (going from airplanes and ballistic missiles to orbital space flight and then Moon missions).
Consider that even reusable self-landings boosters were being worked on in the 90s, before funding was cut off. And for expandable rockets, virtually all rockets designed and launched in the last few decades have successfully accomplished their first ever flight, launching some kind of payload to orbit.
They are inventing a little, but the basics of rocket flight are now well understood. You can get a university (probably post grad) course on it. And nothing that they are doing is all that revolutionary, definitely not compared to what Apollo did (going from airplanes and ballistic missiles to orbital space flight and then Moon missions).
Consider that even reusable self-landings boosters were being worked on in the 90s, before funding was cut off. And for expandable rockets, virtually all rockets designed and launched in the last few decades have successfully accomplished their first ever flight, launching some kind of payload to orbit.