In the most famous mistake of the conflict, a B-2 bomber put its ordnance precisely on the assigned spot. That the spot was occupied by the Chinese Embassy was a failure of Intelligence, not of airpower. Military armament production is destroyed. Military supply areas are under siege. Oil refinement has ceased, and petroleum storage is systematically being destroyed.
Electricity is sporadic, at best.
Major transportation routes are cut. One of the many errors in Operation Allied Force was telling Milosevic ahead of time that he did not have to worry about a ground offensive. That knowledge no doubt reinforced his defiance. However, even if a ground offensive had been planned, it would have been preceded by an air campaign. The casualties from an immediate ground assault would have been intolerable, both to the invasion force and to Kosovars caught in the firepower of the battlefield.