This "simple" style of writing demands a lot of the reader's and writer's shared context. Even in this comment section you can find two different commenters defending the essay but making different assumptions about what sort of writing PG is discussing! You assume essays, and another commenter assumes business writing. I happen to think you're both wrong, and that Graham's "Write Simply" prescription is meant to apply to much more than just business writing and essays (perhaps even all writing, but at least most writing).
Three people who know a fair amount about the author -- at least relatively speaking -- can't agree on the meaning of this essay.
Now, consider that some other people reading this essay might be genuinely confused about why we're discussing Parental Guidance.
I think he is talking about a lot more than essays and business writing. Beyond that, I can't say much. I do not know Paul Graham and haven't even read all of his essays. There are certainly people who don't like Shakespeare's style. I don't know if Graham is one of those people.
He could have written a slightly clunkier essay that allowed me to understand with greater detail the entire collection of types of writing that he is discussing. He didn't want to write that essay, which is of course fine.
To be clear, I'm not "for" or "against" any writing style for the same reason that I don't get into religious wars about programming languages. I think this is a good essay with some solid advice for many different types of writers. But it's also, ironically, an essay that can be used to demonstrate why one might sometimes choose to write a bit less simply. Or, to write simply (plain words and simple sentences) but without trying to "jump into the reader's brain without them noticing".
It's really the combination of "Write Simply" and "saltintesta" that I think deserved at least a bit of a "well, sure, but realize this approach can be a footgun".
Three people who know a fair amount about the author -- at least relatively speaking -- can't agree on the meaning of this essay.
Now, consider that some other people reading this essay might be genuinely confused about why we're discussing Parental Guidance.