There has not been a lack of AI progress in the past 30 years, but rather some sort of 'True Scottsman'-esque raised expectations phenomenon. Natural language processing, computer vision, etc have seen dramatic improvements in recent years but every time there is an improvement people say "well that's just standard stuff, not real AI". As long as a technology is real, people seem weirdly unwilling to accept that it is also an example of AI. The "real stuff" seems to include "fictional" as an integral part of it's definition.