You risk it when there are no people on board to find the issues. Fix issues, rinse repeat.

NASA/Congress pushes the armchair quarterback approach. Analyze forever, fail because analysis isn't the same thing as real world experience, get stuck using 50 year old rocket technology. Each engine on SLS cost more than the entire Starship super heavy launch vehicle.

By weight the RS-25 engines cost about 70% of that of building their 7000lb mass dry mass out of gold. That's insane.