This is just untrue. Dairy was not produced differently in some ancient past. It's produced differently today, in many places, and recently even in the states. Factory farms have small cost advantages and (imo more significantly) financing advantages. Non-corporate farmers can't tap into private equity markets, bond markets and whatnot like corporate farms can.

Anyway, decent farming is as possible today as ever, even moreso. Dairy would not be a luxury item, it would cost slightly more.