(For anyone else confused like me: codeulike is replying to a different, dead comment by the same person.)
Let me continue here.
Henry Spencer at least helped to popularize the idea (if not invented the phrase himself), that Space Shuttle wasn't reusable, but rather refurbishable system. Both 1st stage boosters and 2nd stage engines had to go through detailed inspection and maintenance after each flight.
I'm a bit baffled as to how you dont see how Falcon 9 and Starship are different to the shuttle. Much more re-usable, must faster turnaround. And hence much cheaper cost per kg to orbit. Granted that Starship might turn out to not work (Musk likes to gamble, thats what innovation _is_) but even Falcon 9 is reusable in a much more comprehensive way than the SLS ever was.