So what? The people in the past had less information to go on,...less to work with to figure it out.
And they were right. Every generation is worse. It is an ongoing march to destruction that gets closer with each generation. No one who knows what they are talking about ever said that it needed to happen within one generation. One generation isn't that long.
There is also an acceleration factor. The closer you get to the end the faster things happen. Then there are linchpin moments where it makes sudden jumps, but if you are living in that moment you don't recognize the significance. One example of that is the 1960s with the Sexual Revolution,...but people back than never thought we would be in the men -vs- women disaster we are in today because of it. Then the USA exported it world-wide. So the Sexual Revolution went from being a local phenomenon to a global one. There were other things like, the rise and fall of the Greek Empire, the Fall of Rome, the two World Wars, the Fall of the Soviet Union. They were all unexpected and then they just "happened".
The Roman Empire lasted over 1000 years (well over 10 generations), but at year 800 people would have been "poo-poo'ing" the predictions of it's fall saying, "Well it has been going for 800 years just fine and we are still going to keep on going like we always had been". At year 900 they would have been mocking them saying,.."They've been saying this crap for 100 years and we are doing fine! They are just fools!". But the fools were right. Rome would have never lasted that long had they had modern mass media, social media, the Internet, etc. All of those things create an acceleration.