system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is lacking from modern CGI that allows humans to still distinguish it from real objects on film?
gpt
You only notice it on people because you have tens of millennia of refinement in your brain to spot the subtlest differences in people to find something that isn't quite right and could signify danger.  Subtle things from not moving quite right for the body they have, to slight shine off the face, to hair not falling quite right can throw up a flag in your head that indicates something isn't quite right here.

You don't see 99.99% of digital effects in movies.  Cars, planes, buildings, and really anything artificial can be added in by a computer without you noticing.  Cars in particular are easy because they're always shiny so a slightly too shiny CGI model just looks freshly waxed.  Buildings are also reliable because they're not moving and the lighting never changes.

Basically no one is blowing anything up these days, its too easy and cheap to just add it in post.  You don't notice CGI these days, you think its practical effects which is the biggest compliment you can give it.