That might not be the intention.
Given the chaos of life, and especially the chaos of WW2, isn't it a little ridiculous to tell stories about it that are neat and clean and have a coherent logical flow? If humanity was like that there never would have been a WW2 to write about.
I wouldn't want to only read Pynchon, but given how often we dream it makes sense to read a book that follows dream logic sometimes.
It captures a very real part of the human experience that more plot or message focused literature leaves out.
There are whole genres of music that are often characterized as "just noise" or "boring" or whatever by people who haven't put in the work to learn how to appreciate them. Some genres seem to be much easier to learn to appreciate than others. Some are famously difficult.
Books work the same way.
So, in the first sense, I don't think it is "bad" because I believe this is exactly what the author was setting out to do in writing it. In the second sense, yes, it is a bad book in that I don't like it.
With Gravity's Rainbow, when yet another scene is resolved with kinky sex and the overriding narrative arc turns out to be an elaborate dick joke, you get the feeling this might literally be true!
(Really, GR frequently reverting to the trying-too-hard to shock or the scene resolving by the protagonist getting laid or inebriated is much more annoying than the stream of consciousness style narratives, flowery language, inability to suspend disbelief or general mystery about what's supposed to be going on, which are more widely used literary devices...)
Also: for those who like Pynchon, and would like another author whose work requires chewing, give William Gaddis a go.