Recently switched my dogs to insects after going through about 10 different diets. They're greyhounds, which have notoriously delicate constitutions. What worked really well is a kibble made from mealworms. Not wishing to be disgusting, but their shits sent from pancake batter to "completely normal" within a few days. Apart from a few occasions (where one of them foraged raspberries from our garden) they've been great. Happy, energetic dogs with shiny coats. As a vegetarian (for ethical reasons, mainly climate change) I'd consider adding them to my diet if I could get them at a reasonable price. Technically they should be cheap, but they're ridiculously expensive if you can even get them.
And since we still don't know "everything" about human metabolism and it seems there is some significant differencies between ppl, the real question is "what would be the long term health impact on the whole population, namely over several generations?"