I’d suggest it is unhealthy. We don’t even know what all is in the food we eat, so to pretend we can combine a bunch of synthetic stuff into some well rounded meal for daily consumption I believe is dangerous.
2. Some people have been on 100% Soylent diets for years now. I don't believe there's been any indication of nutrient deficiencies yet.
3. This argument seems weak because you don't know how unhealthy the diet you're replacing is. If I grab a Soylent for lunch instead of getting a burger or pad thai at the food court, which is healthier? Are the high levels of cadmium in spinach unhealthy? How many naturally occurring carcinogens in natural foods are still undiscovered? Any diet has risk. You need to show why Soylent is worse than what it's replacing.
Soylent is at least somewhat balanced. Everything is in a ratio that someone at least actively looked at. When I cook up a meal it certainly isn't.