Personally I think intelligence is trainable and a part of the reason we do not see more intelligent people is because the RoI of scoring well on tests and IQ tests drops off pretty quickly
You are good at what you do frequently. If what you do frequently has low RoI in terms for satisfying your desires, you should stop doing it and do something else.
I'm sure someone more knowledgeable can chronicle the use of polymer frames in firearms, which maybe really caught on in the 1990s?
Failure to improve on old designs seems like a good thing to me as a consumer, it's preferable to churn