True. But we aren't infant cows. We have different and more varied needs. So I guess I'm wondering what milk would be like if we designed it for weaned humans, in various circumstances.
Soylent, Huel etc... admittedly they're made out of various plants rather than growing their proteins etc. in a vat.
True that we aren't infant cows, but we're very close. There aren't many nutrients that we need but they don't, or vice versa (vitamin C is an exception) -- the bigger difference would be in relative amounts. You can live quite happily for a long, long time on a diet of bread and cow milk.