If you come from the future and the best investment vehicle you can think of is a 401k, you don’t deserve to be a time traveler.

Maybe it’s not the best, but it’s the correct one. Clearly future self knows something we don’t

In before future self just forgot to check and is just trying to make the best use of it

My headcannon is that he’s already come back several times with amazing investments and it turns out it goes bad every time. He just ended up going for something more reasonable/healthy cause nothing else worked.