Delay happens. Mismanagement causing no radar not even old ones is just extreme case. When did 60s China do it? When did Soviet Union do it? Europeans? This is absurd stuff. When did it last happen in US that cause fighter jet mount dead weight radar?
F-4s had such episode off memory in late 1960s.
F-15A wasn't far from failure with it's advanced radar, but they managed to get it working more than not(actual reliability took a few years more) just in time.
Most prominent such delay in recent US history is of course AMRAAM, which left huge F-16C(and A) fleet effectively incapable of BVR until after the CW.
Now it's jokes and distant memory, back then it was almost a disaster, because all relevant migs most certainly could.
Overall it's called technical risk, there's no way around. And making a risk decision in arms race/development is of course a risk in itself. But US are heavily reliant on staying ahead of the curve(and, almost more importantly, being perveived as such) since WW2.