Plynck, I would disagree with the word “evidently” in your post. In the thread you reference Antonius Block gives a good review of the history of the painting and given that Nava never gave a cite for the claim that it is a “printing plank”, I find his post more persuasive.
This post from later in the same thread disputes Nava’s claim about Guernica, and the immediately following post from the same poster provides a possible explanation for her confusion. Absent a cite supporting her position, I’m reasonably comfortable in dismissing the “printing plank” idea.
ETA: Apparently, I owe JohnM a Coke.
Picasso was definitely interested in “primitive” art. Mostly African.
I’ll leave the “stupid” up to you…
(According to Wikipedia, Picasso’s “African period” was earlier than Cubism. But he didn’t abandon styles just to satisfy categorizers of art.)
Thanks folks, and sorry for perpetuating that. I “evidently” 
didn’t read the thread much past that post, not having a lot of interest in the painting.
Because it looks stupid, fucked-up, scary, “off,” weird, eerily amateurish - all things that come together to form a terrifying portrait of a bunch of people and shit getting blown up. Effective.
…but could a child draw/paint it.
NO!
It’s 137.4 × 305.5 inches big.
This is a hugely important factor. We can look at a reproduction of it on our screens and see how it’s all laid out. But that’s not fair to the real thing. It has no single focal point, in fact everything is laid out in a way which drags your attention from one object to another incessantly. The swooping faces on the right, the bull to the left, the light bulb and the sprawling corpse. There is a focus on extremities, the broken sword, the twisted hands and feet.
It sounds like such a ridiculous cliche, but even though I’ve looked at (reproductions of) that painting so many times, I still see new things.
Then doesn’t that answer the question in your OP?
[Note: I am noticing you may not be able to reply for a bit, but if and when you get back here, I would be interested in your response - perhaps there is more you are looking to understand?]