I would not subscribe to any newsletter written with AI. Why would I do that? The "content" so generated is almost by definition average or median. It will also be nothing new, by definition, but instead a rehash of other material the model's been trained on.

Now that I think about it, any organization or entity that makes a newsletter with AI/LLMs is probably creating "content" just to fill up space, for SEO purposes or some such not-even-nefarious, but rather dull and boring, reason. I'd probably ignore their newsletter and "content" accordingly.