You don't need to fully understand what is in a Vangaurd target date fund to have high confidence that it isn't a ponzi scheme that's going to go to zero. You can't say the same thing about the ultra-exclusive off the market opportunity that some business manager wants to put you in.

For a pro athlete looking at making millions for a few years and then facing a sharp drop-off thereafter, a Vanguard target date fund is probably not close to optimal. But you could do far worse and many do!