The whole point of the endermen is that they have no soft tissue surrounding their jaws: seemingly no muscles or lips. That's why they look so spooky when they're angry and they open them. Here though, while the supposed enderman could open the mouth pretty wide, you can see that a big part of his jaws are covered by soft tissue, so it just looks like an ayy lmao. Also I would complain about the eyes not being purple enogh but there's actually a bug in some versions of minecraft where if you look down at them their eyes turn white so it's not inaccurate.
Test cool . But minecraft ... ?!
You seriously play minecraft ? 😂