You'll note that Elon Musk made his first few millions in a "YC-style" web-only company - Zip2 - that had nothing to do with changing the world.
Maybe starting a company with the ambition of SpaceX and Tesla is fundamentally incompatible with something like YC. I don't know. But YC is still useful if it enables the next generation of Elons to make their first hundred millions.
Not that the parent or Sam are necessarily coming from this angle, but one could argue that YC is developing the future Elon Musks of the world by helping talented people practice starting businesses solving smaller scale/toy problems (in comparison).
Maybe starting a company with the ambition of SpaceX and Tesla is fundamentally incompatible with something like YC. I don't know. But YC is still useful if it enables the next generation of Elons to make their first hundred millions.