In addition to the sibling comment, which I agree with [edit: the one starting with “people who generate entire blogposts with claude probably do not care about substance, tho”], I want to add another point. Even when the substance is key, the delivery has a quality to it that encodes a useful signal.
To illustrate what I mean, imagine two blog entries on the same subject, but one is written by an expert on the subject and one by a layman. As humans, we can generally (not perfectly) tell which is which. The expert will write in a certain quality that comes with expertise and is genuinely difficult to fake without it.
LLMs disrupt this pattern. LLMs are able to write with the expert’s quality even while writing bullshit. I don’t mean quality as “measure of goodness” here but merely a set of traits or properties. Humans reading LLM text are far more likely to misjudge the author’s level of expertise.
The next step is unscrupulous humans exploiting this to trick unsuspecting readers into misjudging a text, and now you have an internet where you can’t trust anything anymore, at least not at first glance. Even relatively discerning readers now have to waste time reading more of the text before being able to dismiss it as having substance of little value.
So, as I see it, the upset is not simply from AI provenance of a text, but from this level of dishonesty and subterfuge, coupled with the helplessness with which we’re exposed to it.