It's not merely inefficient, it has a negative efficiency; the more you do it, the less food you have. To produce meat, we have to feed animals. To feed a combined biomass that dwarfs all wild land animals on earth, we need to grow food with agriculture. Growing food to feed to animals and then consuming the meat results in a net loss of food as compared to just growing the food. Every step up the food chain represents enormous losses. Animal ag does not produce food. I know that is hard to accept but it's a unescapable thermodynamic reality.

The reason animal ag has exploded so much over recent decades is that it allows industrialists to capitalize the vast surplus of food that is grown. More food is grown than humans alone can possibly eat. But capitalism demands constant growth, or it eats itself. Animal ag creates demand for this surplus food. It doesn't benefit anyone except the industrialists who exploit both us and the animals. Even returning to 1950s levels of animal ag intensity would slash its footprint to a barely significant fraction of what it is now. It's an absolute catastrophe and people are conditioned to completely tune it out.

We need food, but animal ag consumes more food than it produces. Grazing and other forms of "resource upcycling" cannot make up the massive difference.