As you said, the internet had slop before AI. It has been that way since SEO and social media started to dictate what people consume. Remember Elsagate? Remember the IRA bot farms? Remember NFT monkey PNGs?
Most books were trash before the internet, and most paintings have been amateur since the dawn of painting. We just don't remember those examples because we only preserve the best from each era.
Even if 99% of books published in the next 50 years turn out to be AI-generated slop (which is probably what's going to happen, to be honest), that 1% would still be more than you could possibly read in your lifetime. That goes for music, video games, and visual art too.
Let the AI bros make their slop. They are of no consequence to actual culture in the long term.