Engines & Drag
Correct: the jet was usually clean (no stores), although we always had the inboard pylons...pretty draggy. Start with 12,000 lbs internal, and finish the sortie with about 1500. (45-55 minutes).
The F-22 answer is: relatively clean airframe (drag-wise), and humongous engines.
F-4 was moderately draggy, and the engines (big for their day) didn't have the thrust-to-weight-to-DRAG ratio the F-22 does. The F-22 has enough thrust in Mil to do what I could not in burner.