Store bought papaya are about as good as store bought carambola... for that matter just about ALL store bought fruit stinks nowadays I think because the growers are rushing fruit to market to be first on the shelves. Pluot/plumcots, apricot, peaches, nectarines, strawberries, grapes, pineapple in fact every fruit I buy in the store is lackluster and nothing like the fruit I ate in years gone by.
As far as papaya goes, I don't think it's the cultivar, I think it's more related to them being picked green rather than ripening on the plant because I grew seeds from the store and while the store bought fruit was terrible, mine have always been delicious. My dog agreed with me and would eat as much as I would give her :-)