It's neither. Only the thumbnail background is AI generated.

The look of the page -- that's Substack's default UI, you can't control it too much. The other images are created by me.

I'm simply curious what parts give that "cheap" look so I can improve. On Reddit I've had massive amounts of downvotes because they guess the content is AI, when in fact no AI is used in the creation process at all.

One guess I have is the bullet points + bolding combo. Most AIs use a ton of that, and rightly so, because it aids in readability.

Yeah, I think those things do add to the impression and you should get rid of them. I'd suggest gluing some of those shorter paragraphs into longer ones too.