Or to put it in your analogy, If I feed my cat milk, they'll throw up. That doesn't mean milk is unfit for human consumption.
If AI generated stuff is so bad you cannot train AI with it why would humans use it to train themselves (aka learn stuff)?
a more relevant analogy for llms is a bullshiter that don't know shit about anything but like talk about everything and they're good at that (talking like they know), I'm sure we all at least know or knew in the past someone like that.
at a low enough percentage these bullshiters can thrive and get praise from other people but when there a lot of them and not enough of the real deal, well everyone is in trouble including the bullshiters since they no longer have who to mimic.
This space is where the Venn diagram of marketing and genocides overlap.
At least this is what our specilist at the hospital explained to us.