The era of the production line perhaps? Although, if this is true, then it begs the question what has changed that the most successful companies no longer bulk

The era of the production line perhaps? Although, if this is true, then it begs the question what has changed that the most successful companies no longer bulk produce what is cheapest/most modular/has the most features? Because we clearly haven't stopped mass producing things. I would guess not, so this is academic.