IMHO innovation isn't linear: when you discover something new (say the combustion engine for example) you make great progresses at first but then you spend decades or even centuries refining these progresses.

Add to this the office politics, corruption and big players crushing any hint of competition and you have general stagnation.

I have read about the eventual failure of the F35 for years now. The naysayers had solid arguments but were ostracized by people with conflict of interest.