I would point out that it isn’t really 40 years of development, to be fair. For a variety of reasons we basically stopped or slowed development and upgrades for a great many systems and categories roughly 20 years ago. Unfortunately, one of the reasons given was that “we are so far ahead that the other guys won’t catch up any time soon.” Even more unfortunately, there are no shortage of people here on FR that continue to believe that despite the world steadily serving up proof that reality disagrees.
Hopefully Skunkworks or similar black budget military capabilities are continuously working on technological developments and are just not showing their hand.
That said, my faith in our country is not a stock to purchase currently.
I’m aware the F-16 has had numerous upgrades from inception.