A few years back, I had a brief discussion with one of the Shuttle astronauts, and she indicated that on average there were failures of all launches 1 in 100 as discussed by the NASA engineers, not management. She had been scheduled for the next flight after Columbia. I lost contact and don't know if she ever went up, unfortunately I forgot her last name.
Anyway the purpose of the shuttle was to reduce the lifting cost. The designers had many issues that ultimately doomed the program. The public, especially Congress was not in a mood to continue manned mission beyond LEO, so NASA was in a box, change to the shuttle and continue with manned missions or delete manned missions. For whatever reasons they choose the shuttle.
Whether that decision held us back is a mute point, as they had no program or funding. Now we have SLS that uses current technology combined with new technology to continue manned missions beyond LEO, as long as Congress and partners continue funding.
