This rhetoric is old. You can thrive on a vegan diet very easily without this careful calibration you speak of. The same could be said for common western diets with poor nutrition.

It’s true that you can’t just go plant based by just ditching the animal based components: you have to substitute them. But that’s an increasingly easy thing to do these days.

From my perspective, your point can be regarded as a myth.

But even if it wasn’t mostly a myth: I rather spend a little more effort on balanced nutrition than contributing to the immensely violent system that animal agriculture is.