You're propably correct about the feed ratio but cows eat grasses and hay that aren't consumable by humans. In warm countries that's not a problem, people could grow there crops that humans can eat, but in big parts of world (like here in north where I live) grasses are best thing to grow. Also grasslands are best carbon sink we currently have (https://climatechange.ucdavis.edu/climate/news/grasslands-mo...) and you can't have those without ruminants.

Also it's good to remember how much food we waste each year. We could easily feed the world already now but it doesn't seem to be priority for the people in charge.

That said I'm on a same side with vegans, I don't like the current way we produce food and I'd like to see a big systemic change there. But I think vegans don't take into account how complex problems we are dealing with - nature, agriculture's economics and eating habits and nutritional requirements of humans.