If we are at the point where we don't have enough land to support raising livestock for meat, this means our population is too high, not that we're eating the wrong thing.
You can’t have endless population growth forever, it literally violates the laws of physics at some point.
Preventing people from having children?
Sounds pretty misanthropic to me.
Said differently, I hypothesize that it would be more practicable to create policies that influence what we eat and how that food is produced, compared to creating policies that try to reduce population size. If anything, it appears that more advanced countries are competing to gain population so that the machinery of their societies can keep chugging along in the name of growth.
EDIT: elsewhere in the thread I see people comment on multi-use of animals vs plants, and the consequent implication of increased use of undesirable synthetics/plastics if we raise fewer animals. Systems get complex, and their behavior can change drastically in surprising ways if you start fiddling. But fiddling we must.
How about we set the example for those that want to live like us and change our ways. Is it really worth to live for overconsumption and overfeeding ourselves to death? What kind of life are we leading?
This means people care more about their tastebuds than ethics.
Probably not steak and eggs in cheese sauce washed down with a glass of milk.