According to that particular war game, the F-35 was ineffective in maintaining air superiority in a potential conflict with Russia.
Additionally, the current Chinese military buildup involves a vast array of anti-ship missiles, their own 5th generation fighter, ASAT technology, and a massive quantity of conventional ballistic tipped missiles capable of eliminating our use of forward airbases in the Pacific.
But we do own the carpet. 
Further, by the time we have to have it, I would prefer we have something capable of doing the job that is not "on the drawing board."
I would not call it unreliable, but I can grant maintenance can be a lot, but it can be that way for any system. While ending the program is not going to mean we are no longer a superpower, I think it does diminish our power, at least in the short term.
I am all for the droid as well.
No doubt he will capitalize on it, any good politician would. I am all for the economy going well again.
Yes it is not likely at present, but I would say we do not have the luxury of assuming it will never come. I would say we need to constantly stay one step ahead of them or the situation becomes more likely that a crisis could erupt.
I still would make the argument that the benefits from going could easily outweigh the costs.
