Even if already having a Schengen visa -- or even if not needing one -- a scheduled 5 hour transit would involve me budgeting the time like this even if considering going into central Paris on such a transit:

Up to around 20 minutes to get into the terminal after boarding door opens at CDG (possibly worse than that, if getting unlucky and having a deplaning involving a bus).
Up to around 40-75 minutes to clear CDG entry passport control and CDG exit passport control
Up to around 30 minutes to clear security on return to CDG
Wanting to be at the gate 45-60 minutes before departure

That alone could be up to 3 hours of the 5 hour scheduled transit being taken off the slate. Add in the up to c. 80 minute roundtrip time for a car to go from CDG into the city and back to CDG.

In other words, there's not a whole lot you would be doing on such a short transit going into the city even if paying for a relatively expensive taxi/car ride to go directly from the airport into the city so as to get a "from-the-car" tour of some sights from the outside/distance.