comments to sci-fi geeks in the 50s saying that we would have flying cars and jet packs and hoverboards and all other types of new tech. How long did it take to go from the idea of the instant communictor from the first Star Trek series to the smartphones we have today?

You are talking about people who didn't give a single sh-t about predicting the future and just made up random sh-t, real futurologists predicted rise of internet, predicted AI, automation, VR, Mars mission, predicted accurately almost everything that has happened up to this, point. What you are talking about is based in childish fantasies not facts, you seem to not be fallowing the fact that Googles search engine was recently taken over by a low level AI that is constantly being updates and currently has intelligence of an ant, funny sh-t as 10 years ago we didn't have any AI at all, 9 years ago smartphones didn't exist, 4 years ago drones were used only by military. Ok, what you keep ignoring is that when future comes it becomes obvios and you automatically forget what life was like 10 - 20 year ago, what progress has happened since then, AI that are superior to humans will without a doubt exist in 10 - 15 years, most intelligent predictions are at 2040, why? Because time will be right, we will have so much computing power that existence of advanced AI will be inescapable, if you have matches you make fire, timing in tech world is everything. Why wasn't VR a thing in the 90's? Because tech was too sh-tty and weak, we didn't have the power or 4K displays, timing wasn't right, same as with AI, read up on some real futurologists not that made up sh-t you were mentioning here.. flying cars my ass.