The accurate if unexciting answer is "it depends".
With modern sensors, cockpit and weapons, the F-4's ability to carry six-to-eight missiles and still go fast could be valuable in the long-range fight, particularly against less heavily armed adversaries.
On the other hand, if it turns into a close-range turn-and-burn fight - well, there is a reason the F-15 and F-16 were developed in the first place.
Back in the 1980s there was a serious plan to fit the F-4 with the PW1120 engine from the Israeli Lavi. That would have been quite the aircraft...