All of those have (more or less) strict rules imposed on them to ensure the end recipient is getting reliable information, including being able to follow information back to the actual methodology and the data that came out of it in the case of journals.

Generative AI has the express intention of jumbling its training data to create something "new" that only has to sound right. A better comparison to AI would be typing a set of words into a search engine and picking the first few links that you see, not scientific journals.