Sometimes the answer isn't that simple. The Pentagon loves to "do more with less" and wants platforms capable of multiple options (recon, fighter, attack, interdiction, etc) instead of a sole source platform dedicated to one mission. A jack of all trades kind of thing. Good at many missions, but not great at one. Take the A-10 the F-35 is slated to replace. Single mission aircraft designed to destroy ground targets and is likely the best aircraft ever designed to do such a mission. However, it's being replaced by a questionable machine that cannot perform at the same level.
Sometimes do more with less hampers combat effectiveness rather than enhances it.