Theres more than just gravity to take into consideration. Earth also has a denser atmosphere, while the moon is practically a vacuum. Its like how trying to run under water takes way more force than running on land.

I can kind of see what you're saying about caring less about the laws of nature further away. We know a lot about black holes from observation and calculations, but nobody has ever passed through one and lived to tell the story.. Also, whatever spacecraft they invent doesn't have to function in reality, so they dont have to take physics into consideration. A movie like Interstellar allows creative license to make up whatever science-(fiction) works with the story. Its not a documentary.