There is no need for the A-10, or any other weapon system, to be used all by itself.
In hostile airspace, the EA-18G Growler brings the AGM-88 HARM, assuming those modern air-defense emplacements haven't already been hit by cruise missiles.
Plans for war get ruined upon contact with the enemy. Pessimists will assume that friendly plans get ruined, while optimists will assume that enemy plans get ruined. Asset diversity helps everything except logistics. Success or failure of a reasonable weapon system (the A-10, not knights on horseback) is far from certain. All sorts of unexpected factors come into play.
In a conventional war, "this weapons system works perfectly after we completely dismantle their air defenses" sounds pretty similar to "this works perfectly after we win", IMO. And, theoretically, the F-35 can be used for operations before that happens, which is part of why they're being put into service.
Not to mention "this plane works fine if we get the Navy to do the hard part first" is going to go over well with a rather limited subset of Air Force personel. (The Air Force has wild weasels too - generally F-16s though I believe the F-35 is planned for that role in the future)
In hostile airspace, the EA-18G Growler brings the AGM-88 HARM, assuming those modern air-defense emplacements haven't already been hit by cruise missiles.
Plans for war get ruined upon contact with the enemy. Pessimists will assume that friendly plans get ruined, while optimists will assume that enemy plans get ruined. Asset diversity helps everything except logistics. Success or failure of a reasonable weapon system (the A-10, not knights on horseback) is far from certain. All sorts of unexpected factors come into play.