To get protein you need from plants alone, it usually comes with far more carbs than you need.

For example, quinoa, widely considered the very best vegan protein, as it is high in protein AND contains all essential amino acids to build proteins (most plants don’t):

At 225lbs or roughly 100kg, Yeoli needs .08gm/kg of protein per day, so 80gms (and that’s to maintain muscle not build, so he needs a LOT more). To get 80gms of protein from quinoa youd need to eat 8 cups (I could not eat that). With 320 grams of carbs. And that is one of the best sources of plant protein. Beans and rice, another complete protein together has tons carbs. Beans and corn, tons of carbs. Lentils, tons of carbs.

It is a carb fest. Read about lectins sometime too. Our bodies are made to consume some animal protein. Just adding eggs, fish, or a little animal protein helps greatly.

I would argue that benefits to a solely plant-based diet are limited, not “legion”.