I doubt if a landing slot at CDG is the issue, it's probably the fact that Aerlingus needed an extra parking stand in the non-Schenegen part of Termnal 1 for the Cork flight.
Cork Newcastle seems to be doing exceptionally well this Winter. The Jet 2 Flights are at an optimum time for a weekend break.
Not sure why Brussells isn't as appealing although it once had the image of being a City for Business rather than pleasure.
The only other weekend break choices on Friday's from Cork are London, Paris or Amsterdam and many people have been to these cities already. There's no doubt that Cork people who fly from Dublin rather than Cork for trivial reasons are making it very difficult for the Airport to attract new routes.