Why do you think the Lord made a system where everything eats each other?
I think you need to brush up on your Genesis. A long-standing theological stance that Genesis teaches vegetarianism has always been present within Judaism and Christianity. Eating meat came as a result of sin not before it. Just like child labor became painful as a result of sin, not before it.
All that's happening with people who stop eating meat is they're figuring out the sin of it and stopping before everybody finally catches on. I think those people are ahead of their time.
But if someone were to make the contrary argument, I would counter with this-- just because you can do something doesn't mean you should or have to. And as your love grows even though it might be okay to eat that animal, you won't because your love has grown.
Why would we change now though? Because survival and thriving is possible without eating meat now that's why. I would argue that its the natural progression to stop eating meat now that our own survival does not require it.
"Every moving thing that liveth shall be meat for you; even as the green herb have I given you all things. But flesh with the life thereof, which is the blood thereof, shall ye not eat. And surely your blood of your lives will I require; at the hand of every beast will I require it, and at the hand of man; at the hand of every man's brother will I require the life of man. Whoso sheddeth man's blood, by man shall his blood be shed: for in the image of God made he man.".
The principal we would be discussing theologically is God's conditional will with God 's actual will. God simply must meet humanity where it is so conditionally all kinds of things are allowed, but over long-term wouldn't be as we grow spiritually and can handle a higher truth. An example of that would be divorce under Moses being allowed and Jesus ratifying that and making it harder under the new and higher covenant.