This range is against bomber/tanker target in head-on intercept. Against fighter in chase will be much, much smaller. There was project on design stage with IR or dual IR/SARH seeker, but it was chosen to use only SARH seeker.

Mind you the overall weapon system is impressive: Most SARH systems can only engage one target at a time – the Mig-31 can fire all of its R-33 at separate targets nearly simultaneously (overlapping flight times)!