Replacing food with Soylent is weird.

And also potentially dangerous to your health. The idea of a uniform "human chow" makes sense and has legitimate uses, and we have a paleo precedent in pemmican, which has a reputation for sustaining people in polar environments in good health when they didn't have access to fresh food. But then pemmican uses natural ingredients. By contrast, I worry about ingesting Soylent if the recipes incorporate the wrong stereoisomers of synthetic organic molecules that the body's enzymes won't bind to for metabolism.

In fact, that's my impression of lots of LW-style ideas, such as cryonics

Uh, guys. LW didn't invent cryonics. And for some reason it hasn't registered even with most cryonicists that some neuroscientists think that cryonics deserves a second look because they have the tools now to study the integrity of attempts to preserve the brain's connectome. Refer to the website of the Brain Preservation Foundation.