So first there is a difference between reduction of meat products and an elimination. Having people consume less meat is good and helpful even if they don’t cut it out completely.
Second, as a vegetarian, I don’t understand what you mean by producing a bunch of monocultures. Do you think vegans just sit around all day eating avocados? I eat very little dairy or egg, and my diet consists largely of beans, rice, chilli, bread, stir fry, tofu, peanuts/legumes, veggies, baked potatoes, sandwiches, etc. I eat a large variety of staple goods cooked into a variety of dishes from around the world, and classic American fare, just without meat. Avocados and other resource intensive crops like almonds are a minority of my diet by a large margin. Things like beyond meat is also an infrequent treat.
Edit: here’s a decent article. https://www.nytimes.com/article/plant-based-diet.html
Generally speaking, a plant-based diet consists largely of vegetables, fruit, beans, legumes, grains and nuts, with little or no meat, dairy or fish.
Yet another major study has recently been published, showing that eating a plant-based diet is significantly better for the environment than eating a meat-based diet.
The research, conducted by Oxford University, found that people who follow a meat-free diet are responsible for 75 percent less in greenhouse gas emissions than those who eat meat every day, and that following a low-meat, vegetarian or pescatarian diet is proportionally less detrimental to land, water and biodiversity than a meat-heavy diet.
Referenced research: https://www.nature.com/articles/s43016-023-00795-w
I need to start using old batteries in my bathroom scale.