You can entirely replace animal protein with a combination of plant-based proteins. Ethical or humane methods of killing animals is a step forward, but it absolutely is not required.
I'm not saying that there aren't tons of people who are very healthy vegetarians and vegans (some of them healthier than they would be eating meat), but I'd just like to point out that it's not universally true that you can replace animal protein with plant-based protein and be healthy. Nutrition is a complex topic, and not all bodies behave the same when it comes to food.
Soy is obviously not the only plant protein. My current favorite is mushroom-based, but it is new, and industrial food doesn't have a good track record.