"In responding to Sagan, Thorne pointed out that venturing into a black hole, with the hope of finding a spatial shortcut to elsewhere, would not be a good idea. Astronauts would be stretched like taffy due to its intense gravitational field, bombarded by lethal energy released by infalling matter, and accelerated to a dangerous level like the most unsafe thrill ride imaginable."

https://lithub.com/the-physics-of-fiction-how-art-and-science-inspire-each-other/