Just to add on, if you don't mind: the SLS uses four RS-25 engines, the exact same engines that were used on the Space Shuttle (admittedly, there is a plan to improve them later), as well as solid rocket engines that are derived from the Shuttle SRBs.

I actually do think that more than one US-based provider of space launch systems is something important, but it's wild to me that mature US launch systems can basically be cleanly divided into "companies trying to sell the same technology to the government for the fifth time over fifty years" and "SpaceX."