And then you get to teeth, which are like wet rocks. You're building this thing that is going to bomb if it can't do soft, meaty, hairy things convincingly and then there's this itty bitty section you're only going to see sometimes that is a dark membraneous cave full of wet rocks.
My guess is that teeth haven't been that interesting to date and that the modellers don't have access to hundreds of reference pictures / geometries of teeth for their modelling. As opposed to reference images of skin textures, etc. Tongues are probably the same. In fact I don't think I have ever created a render of a figure with their tongue out.
Once they take the time, the teeth should be easy to improve.
Some form of subsurface scattering[1] is a must, and not easily done in games/apps because you can't really "bake" it like you do for most other textures to run performantly.
[1] https://en.wikipedia.org/wiki/Subsurface_scattering#:~:text=....
Subsurface scattering is the correct answer. It's a very small area and a very expensive calculation.
Teeth are translucent and the coloured lighting on them changes rapidly.
Technically speaking an animator might know. A lighter would have a better idea. And finally a shader writer could tell you exactly.
If you were interested in the more technical breakdown of responsibilities in the industry: (of course it'll change from studio to studio, but this is pretty good)
https://discover.therookies.co/2019/05/22/job-titles-in-3d-a...