Earlier quoted context omitted.
Which would be very compelling if your body only needed calories to survive. Meat is the most efficient way to deliver proteins and essential amino acids. You should also dig into the concept of bioavailability.
This is debunked. Tofu is incredibly protein dense - on par or surpassing chicken breast. Without looking it up and subjectively, tofu also seems to be digested very easily. There’s also seitan and the beans. Nuts also exist but have fat/protein ratios that tend toward uncomfortably high. (If what your eating has macros that approach the fat content in nuts to other nutrients that’s pretty high and should be noted.)
The bigger issue is vitamins, in particular B12. But that's easily fixed with a daily multivitamin.