I am always a bit cautious, when I listen to arguments from competitors, who compete with Google. Is it an argument or marketing speech?
First of all, Google is not the internet. Is providing search results a challenging business? Yes. Could do Google do a better job? Yes, so could do others. The fact, that Bing does not gain market share even though pushing everything ChatGPT related may confirms this notion.
Content and consumer habits changed.
In the 90th, website where dominated by text. Compared to today, every page that was suggested by Google resembled a book. Today most websites look like easy to consume snippets due to lower attention span, less time.
Then came Twitter, TikTok, Facebook etc.
So I would not blame Google in the first place.
Will ChatGPT replace Google? Not entierly, but they are working on it.
Will we say the same ("ChatGPT send LLMs into 'spiral of decline'") about ChatGPT in 10-15 years from now? Maybe.