doesn't mean these issues can't be solved. structural issues are easier to deal with, this is not the first time a fighter has required more structural bracing after flight testing. the stealth coating should also be solvable. while the F-115 is not supersonic mainly due to the aerodynamics required to promote radar deflection, the coating has proved pretty stable. it does require patching however this is minor and easy to do.
the fly-by-wire issue is the most serious as the jet can't be flown to it's full capabilities without it. that also should be solvable. in the meantime it will reduce the plane's abilities.
while the operational requirements are vastly greater today, the B-29 was rushed into service during WWII and it also suffered from design flaws. it's requirements were state of the art at the time, in both payload, altitude, range and of course the first pressurized cabin.
it's main flaw were the engines, which suffered mechanical issues in the early versions. that was fixed of course and had the plane had the proper testing lead time it would have been solved beforehand.
interestingly, three planes had to land in Russia as alternate landing sites. Uncle Joe returned the pilots but not the planes. the Russkis are great at copying things and they reverse engineered the plane, including the engine flaws.
of course in a few years post WWII the jet age rendered the B-29 obsolete.
https://en.wikipedia.org/wiki/Boeing_B-29_Superfortress