NASA followed the "we launch when the paperwork weights more than the rocket" model where everything had to be tested to death on the ground. Even so, many people expected the first Saturn V launch to fail, and they only launched a complete rocket because it was faster than testing the first stage with a mass simulator on top. And it was never fully debugged before the program was shut down.
SpaceX follow the software development model where you break things fast, and complaining that they didn't get to orbit the first time (something they haven't even tried to do before this flight) is like complaining that someone wrote some code from scratch and the first try didn't compile. They've also been able to test a lot of potential failure modes (e.g. deliberately removing heatshield tiles or flying more dangerous reentries) because they're flying often and willing to break things.
One result of this is that a single SLS engine probably costs more than an entire Starship/Super Heavy stack. Even the ones that were taken off Space Shuttles and refurbished.