I agree it has gotten better with lines after they have taken measures to limit CC access and to some extent lounge memberships, at least at the skyclubs i use regularly. But inside the JFK B31 Skyclub it was still rammed to the rafters last time i was there and that was after the recently opened Delta One (with as far as I remember a capacity of over 500pax.) and A8 lounges.
So with DL short changing their own elites I fail to see where the hordes in the SC's still come from other then CC and memberships and I am still going to refer to DL as a CC affiliate that just happens to have airplanes My guess is that there are enough reserve cards i Nassau alone to make it a capacity problem for DL at JFK (joke).

Besides of that the new A8 Skyclub is great and much nicer then the ever jam packed B31 lounge, if one doesn't have access to the DL One lounge.