And yes, for an ideal plant-based diet, a couple of supplements (B12, calcium, possibly vitamin D and/or iron) may be necessary. So what? Just take a decent multivitamin - especially if you life weights (like I do).
What is the big deal?
It's still far cheaper, far more sustainable for humanity (about 7-13 calories of feed for every calorie of meat, depending on animal) and healthier long term.
But, if you want to spend far more money, have (on average) worse long-term health and reduce the world's overall food supply far in excess of your meat-based caloric intake...go ahead.