Starters only?
I would take Young over anyone that is broken down and/or over the hill.
So no Rodgers, no Cousins, no Smith, no Flacco. Not that a team can't win or compete but their time is over.
I would take Young over some early-in-career qbs that have had little to no success. This would mostly be a zero-sum trade.
So, no Fields, no Murray, no McCarthy, no Gabriel, no Penix.
I might be forgetting 1 or 2, but that would be the gist.