I mean, it's still a problem in some Hollywood CGI movies, so...
Human faces are as hard as it gets, because we are conditioned to feel we know faces. Cartoonish faces like Pixar movies work fine because they can exaggerate motion, but a human face needs to look and move exactly like we've known faces to look all our lives. There's literally a brain function for recognizing faces.
And the more resolution and effects used to make a digital face more closely approximate a human face, the more we go, "Ugh, that doesn't look right..." The lips don't curl or the jaw doesn't flex or the eyes look dead or the phenomes of syllables don't match the tongue or the subsurface scattering of light on skin isn't perfect, whatever.
It's super hard, because we can see what we expect to see just by looking into a mirror.