Other animals also eat their own vomit and feces. There’s a reason we don’t imitate them.
Do you understand why they do that, though? It’s not because they like the taste!
For instance, rabbits eat their excrement, because their bodies did not digest all of the nutrients on the first pass. Dogs eat their vomit to reingest lost nutrients. Fecal matter is much the same. If an animal is well-fed, they will not opt for vomit or feces as a meal. In the wild, however, that may be the only meal they get for a while.
It’s similar to survival tactics in many ways. Your urine can serve to keep you hydrated in an emergency situation. Your feces, not so much. There’s a reason it’s called “waste.”
Placenta is not explicitly waste, it’s “leftover biomass.” There’s nothing found to be caustic or deadly to humans in after birth, it’s just not something for which we’ve concocted recipes.