nutrients

In the abundance of products in the 21st century you can absolutely get all the nutrients you need in excess without touching animal products, let alone meat.

convenience

Not sure how cooking pea protein sausage is less convenient than cooking a pork sausage. There are tons of vegan/vegetarian convenience products in the fridge aisle. Even if there was indeed some very minor convenience to cooking meat (which I am really in the dark about), are you really arguing your minimally bigger convenience is a good enough reason to kill a living being?

cost

In some way I agree with you here, meat is heavily subsidized while vegetables aren't (at least where I live) and it is a shame. Chicken wings can be cheaper per kg than some kind of vegetables. That's a systemic problem and needs to be taken care of not by the consumer, but government regulations. But a) you know it is bad quality meat that is on the cheaper side, b) most people aren't in a position where you have such financial pressure (food stamps etc) where you have to weigh calories per cent, c) vegan/vegetarian diets can still be cheap af as long as you don't try to do instagrammable kale quinoa brokkoli sprouts smoothies with avocado and chia seed granola or some crap like that. Potato wedges with sour cream are a vegetarian dish. Beans with rice. Noodles and tomato sauce. It doesn't have to get expensive or complicated.