We just wrote a piece this morning in Orbital Index about the iteration speeds of SLS, New Glenn, and Starship. SpaceX is putting everyone else to shame.
https://orbitalindex.com/archive/2021-03-03-Issue-106/#heavy...
Reminds me of this quote from NASA Administrator Charles Bolden in 2014: "Let's be very honest again. We don't have a commercially available heavy lift vehicle. Falcon 9 Heavy may someday come about. It's on the drawing board right now. SLS is real."