I think the situation is more nuanced than that.

Of course, the F-35 program was an incredibly expensive mess (litterally the most expensive weapon program of all time), because of conflicting specs, data leaks, political infighting, cost overruns which are the stuff of legend, etc... At some moments, there were certainly reasons to think the whole program would collapse on itself like wet tissue paper.

But there are operational F35 now. 900+ as of 2023, which is 4 time more than the rest of Gen 5 fighters combined. And performance-wise, it is good, especially on the stealth & avionics parts. On the other side, the J-20 is largely unproven (probably a decent design, but not as good), and the Su-57 is a bunch of glorified prototypes.

Now sure, cost is high, maintenance is time-consuming, availability somewhat below target, but it's not particularly surprising for high-performance equipment. It may fall short of the ambition of the program on the cost part, but by itself it's a dangerous and fully operational fighter.