You're equating sentience with non-sentience. a LLM is a non-sentient program, created by humans to learn language. You are a sentient person who is influenced by the painting techniques of Van Gogh and el Greco. While you don't need to credit them, they have influenced your work. That is entirely acceptable practice.
This is a huge difference in the realm of copyright.
EDIT
Also the works of the artists you mention are in public domain in most countries. They can be used by LLM without incident. Works of artists not in the public domain should be subject to copyright law for LLM.