AFAIK they're far more sustainable since they need nowhere near the amount of land, water, resources and food as the animals in the dairy and meat industries do. This, and further minus all the torture, suffering and force-feeding
Or we could eat like our grandparents used to eat back in the 50s-60s, at least in France meat was still a fairly occasional thing, you bought a good cut of meat every now and then and enjoyed it. Today we chug gallons of processed meat at every meal, most of it being bad on both the nutritional and taste aspect.