That sounds like Socrates’ argument that writing would weaken people’s memories.

Saying it leads to cognitive decline is saying you can’t use an LLM and have critical thinking, which I can’t agree with.

That's not me saying it. MIT, Harvard, and others have released numerous studies that show using LLMs does exactly that, reduce critical thinking. You can disagree all you want but until you do the science you're disagreeing with a growing body of actual experts.