What a weird question, if it was at all genuine. Not only is it not inefficient but, e.g., cows are absolutely unique and amazing for their ability to digest, e.g., grass into something that is highly nutritiously desirable for humans.
Asserting ruminants are “irrelevant” tells me nobody should take you seriously on this topic. Replicating their function is the problem to solve if you ever want to make the case you think you are making.
