having driven to las vegas and back multiple times, salt lake city, los angeles, and driven home from washington, i can confirm that there's a definite line once you get far enough west where it becomes 'interesting'. but if you can deal with it and eat miles, it's worth it IMO.
That said, I think your timeline is ambitious. I'd take more than 2 days to drive to California, and I say this as someone who has done one-shot nonstops from Spokane to St. Paul, Salt Lake City to Minneapolis, Flagstaff to Minneapolis, Nashville to St. Paul, Vegas to Wall Drug, and more.