If you only take into account caloric production yes, meat is not very efficient. But there is a reason humans started to eat and domesticate animals. They provide us with fur, an other byproducts (fertilizer, etc...)
I understand the need to find some substitute with 7 billion people in the planet, but i think grown-in-a-lab meat will probably be a better alternative in the near future.
When people fly airplanes across the world, do they not look out the window and see what I see? LOTS of unused land. As in, most of the planet.
There's plenty more room out there for everything we need. Only political borders (placed by us humans) prevent us from using all available land/resources to provide for all of humanity.
I understand the need to find some substitute with 7 billion people in the planet, but i think grown-in-a-lab meat will probably be a better alternative in the near future.