AiM-54 is not maneuverable COMPARATIVELY! Due to it's weight, size and speed it will clearly be less maneuverable than missiles that are lighter, smaller and slower! but due to it's relatively large payload it doesn't actually need to hit the aircraft to down it!
AiM-54 warhead is 135lb vs Aim-7 80lb vs AiM-120 40-50lb
But if I was Iran and I planned on producing an Air to Air Missile as heavy as the AiM-54 I would have instead followed the Russian in terms of propulsion and would have built various two stage missiles like the R-77 variant's the Russians have
From a ramjet version to a two stage solid fuel versions
And if I had to make them bigger than the R-77 variants to carry a bigger warhead for what ever reason then I would have just made them bigger.…...
Iran's Air Force has no one to blame but it's self in that regard