That's not necessarily true since the plants are different.
That space for grass feeding could be used to grow much more food to feed humans directly.
Weather those calories were going to be used by humans or not that land is now used to feed some cows that will feed a few people. Instead we could use that land to grow plants and feed more people then with cows.
Also, AFAIK, that natural environment where cows are fed is mostly created by destroying forests.
At least in the United States, there is a fair bit of land that is both non-arable and yet perfectly sustainable for cattle (much of this land was historically home of a bovine species, the plains bison, in the first place). I'm thinking areas like certain areas of Texas, Wyoming, Montana, etc.
There are probably other areas in this regard, so I think it's possible to keep some meat and actually have it be relatively sustainable.
Everyone's overall point is correct, however, in that this does not apply to a lot of meat production today; keeping only the more sustainable practices would end up making meat a luxury product (as it was in earlier times).
Sometimes we can't grow crops on that land. And it's a lot of non-arable land.