It means very ordinary. There's nothing to describe about it. Just a typical hotel. Not famous. Not bad, not good. It's a hotel, what more is there to say? The idea here is that they didn't want to choose a famous or obvious hotel. They wanted a hotel that would be "lost in the crowd."
"On our trip we stopped in Collinsville at a nondescript chain motel. I can't remember anything about it. It must have been OK or I would remember it."
"Everywhere President Joe Biden goes, he is accompanied by a nondescript briefcase. Though it looks harmless, the black briefcase contains within it the power to destroy civilization as we know it."
In an old technical usage, "nondescript" literally means "not yet described." It means a species of animal that hasn't been described by scientists and given as scientific name. In normal use now, "nondescript" means not describable, because it is so plain, ordinary that there's nothing to say about it. In contrast, "indescribable" usually means something so wonderful that it is hard to find the words to describe it.