He is literally the proof that writing can be bad (albeit we should define what good and bad writing are and agree on it) but still interesting because of the ideas.
That's good in my opinion - in the same sense that hammer which drives down nails flawlessly is good. PG is not trying to write colorful fiction, he wants to communicate something, and he succeeds in doing so. It is still a hammer, not a statue of David, but there are good and bad hammers, and this is a good hammer. You wouldn't want to drive nails into boards with a statue of David anyway.
I don't share that fully, and I've read every single one of his essays, his arid style gets tough after few paragraphs, it's too dense and harsh, sentences are consistently very short so it feels like reading a machine gun.
That's fine. The ideas transmit, the words are forgotten. He doesn't need to use memorable sentences if he's saying what he's trying to say.
Paul Graham is a very skilled communicator. He's not a writer's writer like YKW, but he doesn't need to be.