I think most people believe that if Carr is on the roster, it's unlikely that Rattler wins the starting job. Some people seem like they want Rattler to be given the starting job no matter what, so they really want the Saints to move on from Carr to clear the way for Rattler to start.
I think there is a flawed assumption to that line of thinking. The assumption is that next year's starting QB will either be Carr or Rattler. It could very well be neither.