A plant based future won't have disabled people in it. It won't have Me in it. I'm anemic and don't digest food right, I require meat with high iron content and iron pills and I require high vitamin food that plant doesn't always have. Like cats, require thiamine only in meat.
They weren't vegan, they were vegetarian. India has the most diary cows of any country in the world.
There's plenty of Jains who are pretty strict, I know lots use dairy but there's always been plenty that don't.