There's a number of places that immediately spring to mind, which used to be popular, but where nobody in their right mind would currently go, such as Acapulco and Tunisia.
Once upon a time, even Afghanistan was a popular stop on the Asian Hippie Trail. Besides weed, Afghanistan’s big draw - excuse the pun - was Kabul. So popular was it in 1973 that Lonely Planet fretted about it becoming a “tourist trap”. Highlights included the city’s markets, parks and gardens.
I even met a retired guy in Greece who used to work on cruise liners, who had taken tourists on an overnight excursion to Sana'a, capital of Yemen, in the 1970s.
So where that's popular now, do you imagine the next generation won't be able to go to, without an armed guard?