You might as well turn these kind of arguments around and wonder why all these experts from all these companies and all these countries never predicted/foresaw and anticipated all the big problems the whole JSF project encountered, why did they chose so many other faulthy, severely underperforming or hideously expensive defense projects in the past.
Same thing goes for so many other sectors in the past, present and undoubtly the future.
In 2007/2008 the vast majority of economists, bankers and affiliated experts never really foresaw the huge problems in the financial sectors and we all know what happened there, don't we?
The list of failed or underperforming defense projects is long and undistinguished, I'm not saying the F35 is already that bad but it certainly is sometimes heading that way.
If it will ever come online in the predicted numbers with all the different forces it will be eventually made to work(by the people in the field), I'm certain about that but at what expense, if we're lucky the future will be a lot like the post WWII era where we never have to use our weapons of war against a truely equal opponent and the F35 will do just fine but I'm willing to bet that a somewhat simpler , lighter and less expensive fighter (a true new LWF) would have been just as good and certainly more maintainable and affordable and most likely in bigger numbers.