Our bodies are complicated. Therefore, nutrition science is complicated, and very much a work in progress. Because people eat various things all their lives in an uncontrolled way, and because what you eat can have impacts on you 10, 20, or 50 years down the line, getting reliable nutritional data is extremely expensive and difficult.
There are many interactions that we still don't understand, unknown unknowns where we don't even know what the questions yet. For example, we know now that our gut microbiome has important influence on our metabolism, immune systems, and overall health. And yet little of this research existed 20 years ago because there was no cheap DNA sequencing, and we still don't know today how what we eat influences our internal ecology. We certainly don't know what eating a bunch of Soylent for a couple decades would do to a person's microbiome, because nobody has ever tried it.
A dose of humility and common sense would suggest that radically transforming your diet based on our current reductive knowledge of nutrition is an extremely risky bet.
The much safer bet is eating traditionally: eat foods in combinations and proportions that our ancestors and cultures have actually tried and tweaked over thousands of years of empirical experimentation and co-evolution.