It's still weird people don't just use spider tingles...
We're pattern recognition machines and we don't need to conciously be aware of all the signs of AI.
It would be like trying to teach an adult how to ride a bike by telling them what muscles to constrict in what order.
With enough time and effort it might work, but it's the worst way to learn how to ride a bike and anyone that learns and only rides a bike that way is gonna fucking suck compared to someone who offloaded the specifics to their unconscious mind and just gives general commands like "turn left".
Tldr:
You can tell when it's AI, because of the way it is.
Trying to get nity gritty and pick out specifics isn't sustainable long term. The only downside is false negatives from everyone needlessly upscaling pictures, but those would happen no matter what.