Well, whether it was USAF or USMC sending F-4s to Desert Storm for a shooting job, it was equally a waste. The difference is that the Air Force could justify that waste, even if the Phantoms it sent were literally on their way to the Bone Yard. The Marines had a ground role and a smaller air wing, thus it could not justify sending the F-4S to that Theater, given that they were confined to Sheik Isa, a couple FOBs and the floating bases.
Since there is no Desert Storm, or even 1980s Gulf War, scenario in DCS, one could easily place the F-4S in ever scenario the F-4E would be present, and more.