Your message is right that you can't spot AI, but from what I've seen professionals by large aren't using AI for from-scratch design.

I do have one way of telling: my wife's a designer, and she has many artist and designer friends so I see how they work first hand. AI is largely used for edits that need to be done quickly rather than from-scratch generation.

You talk about aesthetics but that's very secondary to communicating the precise thing you want to communicate. AI just isn't there.