Rothlesberger went 15-1 and got to the AFC Championship game that year, better than all four of your QBs did their rookie year when they sat on the pine. He then went on to win two Super Bowls, which is more than Rogers or Mahomes (yet).
We can argue it for a while if you want, but really, there is no proof one way or another that playing Mac as a rookie is any better or worse than sitting him. That said, considering the QBs who are available in free agency or as potential trades, the team is better off with Mac by a country mile.