The average person has exactly zero skill at looking at picture details, it's a thing you develop as an artist and then need to consciously break by flipping the image, tilting your head etc. to look at the whole composition again.

The average artist also won't notice when a cow's horns are above their ears (instead of above in front) because they haven't seen a reference cow in ages, and never specialised in drawing (or whatever) cows. The average person without artistic eye does not even have the impulse to zoom in on that kind of thing and literally won't see the little brown hat you put there, you'd have to make it pink for them to ever notice.

Honestly, I don't see anything really wrong with that hat. The back rim looks a bit strange but that might just be because it's a strange hat, and I'm certainly not fashion-conscious enough to spot that it's an anachronism.

The hands and writing are clearly messed up and pretty much the first thing you should have a look at when figuring out whether something is AI. If this wasn't a "photograph" though but an illustration you might also look at a shitty or lazy human artist in many cases. In this case there's a dead AI giveaway as humans would never make that kind of mistake: The shirt. T-shirt sleeves but bare chest? How does that work? Shirt and vest and chest are painted very well, the AI did a good job at the details, thing is it doesn't understand how garments actually work and that the combination of details doesn't make sense.

Or, in short: (current) AIs are quite good at overall composition and lighting, may or may not have their issues with smaller details depending on the detail, and have lots of trouble enforcing consistency on details that aren't directly adjacent to each other. You'll also see things like e.g. the lines of a dunno column being discontinuous at the spots where it moves from background to invisible (because foreground before it).

Many models have gotten quite good at hands (especially SDXL), unless you're trying to do something complicated with fingers grasping into each other and stuff it'll probably get it right. But the list of these things is endless, you'll e.g. see PC keyboards with seven rows of keys. So look at what you know you know (and I don't know jackshit about hat fashion), and check it.

On another note: It's good that the people putting out those kinds of fakes seem to have zero artistic skill. Without AI, with good ole photo manipulation by an actual artist, spotting a fake could be close to impossible. Generating flawless photographs with current AI is also a crapshoot, you'll end up sifting through a gazillion of possibilities, illustrations are way easier because you can explain things away by "yeah it doesn't need to be accurate in that detail, just give off the right impression". If you want a convincing fake you'll still need an actual artist manipulating actual pixels to fix up the AI mistakes.