I see many recycled misheard clichés here, starting by the "red meat is carcinogenic" mantra, that nobody serious has proven still, and that at this point is just pseudoscience.

> By mass, beef alone, outmatches every single land animal on this planet, combined

This is most probably false. To start you are repeating a claim that you didn't really understood. One problem is that you are confusing animals with mammals. Other is that you are confusing animals with vertebrates. In fact, we really don't have decent data on most invertebrates, and almost no reliable data in many vertebrates.

> Cows produce a lot of waste, that ends up in rivers

In the real life, most people use this on fields and agriculture, as crop fertilizers.

And the point 2 is missing a couple basic rules of ecology.

1) Big animals use energy more efficiently than small animals on the same category and,

2) Herbivores suffer a lot of pressure to feed themselves accurately. We can't just eat enough zucchini to replace beef, because we can't digest cellulose, because our small gut is not well adapted to this, and because most vegetables are basically water. The day is just too short.