It's not about fault, it's about actionability. Telling hoards of people they should interpret things differently isn't actionable feedback. You aren't likely to change the behavior of so many people.
But the author is just one person. If that author learned to structure their work better they can singlehandedly improve the comprehension of across the entire mass of readers.
If you're communicating to the masses and they're not getting it, it's your fault. It may not be 100% true, but it's 100% useful to think of things that way.
To give the opposing argument some form of development, reading comprehension is the responsibility of the reader as well.
Some authors are hard to understand, but the message they are trying to convey could be worth extracting.
As a reader it is preferable for you to be able to extract value out of opaque text. The author owes you nothing. And, presumably you are reading because you think there might be something of value underneath.
If you fail to capture that value (If there is any) that's your loss, not the author's.
Certainly, it would be best if the message were communicated in such a fashion that people would not misunderstand it to begin with. But if, and when things are poorly communicated, if you misunderstand the underlying message the person taking a loss is not the author, but you.
To think otherwise would be to focus too deeply on some sort of exposure, or monetary loss on the part of the author, rather than the failure to capture a nugget of wisdom that might be of utility to your life.
But the author is just one person. If that author learned to structure their work better they can singlehandedly improve the comprehension of across the entire mass of readers.
If you're communicating to the masses and they're not getting it, it's your fault. It may not be 100% true, but it's 100% useful to think of things that way.