Ruminants are adapted to eating high cellulose diets e.g. grass not seeds (aka maize kernels) - fully agree corn-fed cattle are not prime beef. Maize feed beef is bland.
Main issue, as you point out is additives, hormones & other allowances (rat hair, faecal bacterial allowances which degrades the quality of certain US foods). USA has some amazingly high quality food if you look carefully.