I've said this in the past, facial projection requires two elements to pull off successfully. Good lighting conditions and a physically 3-dimensional facial surface. Even with the face projection switched off, you still need prominent physical cheekbones, nose, eye sockets forehead etc or else the face will look flat.
I again do not really dislike the Frozen animatronics. But I understand why people find them awkward and even agree to some extent. The faces at least ARE sculpted physically. They have noses, cheekbones, eye sockets etc (maybe certain protrusions could have been a bit more prominent, but they did a pretty decent job here IMO). I think the main problem here is the lighting.
The challenge with projection as a whole is that they work best when the surrounding room is kept as dark as possible. Every additional light added into a scene is an added conflict to this effect and gradually deceases the projection effect's quality, the colors and contrast become washed out, and the image quality as a whole drops. Anyone who has any experience with how projectors work will know this, you have to keep the room in a very dark state or else the effect is ruined. Any amount of light begins to decrease the quality, even reflections and bright surfaces can (including mirrors, walls with bright or white colors, glossy paint etc).
In addition, there's another inherent problem when the light source for the faces is internally projected from the inside-out. Features like the forehead, nose, eye sockets etc won't naturally cast shadows on the facial surface when internally lit like they do when lit by exterior lighting. This can look awkward when the rest of the connecting body is lit externally with spotlights and is casting natural shadows.
There are also areas around the neck and ears that look unnaturally darker than the front face. Like they're connected by a weird shadowy seam, very noticeable from angles where you're not viewing the figure head-on. I assume what is going on here is the shadow is where the internal lighting from the projector has ended. The imagineers have the challenge of lighting the rest of the body with external lights, but they can't get those lights too close to the faces or else it will interfere with the projection, washing out and ruining the effect as I mentioned above. So those shadowy areas are not fully lit and don't "glow" as much as the rest of the body. Hence, inconsistent and unnatural looking lighting in places.
Incidentally, most of the 7DMT figures (except Dopey) managed to largely avoid the shadowy seam, most of which is hidden behind their beards. I think the Frozen trolls' bulbous stubby heads and short fat necks also help hide the seam too, plus their darker blue-gray skin.
Most of the faces in Haunted Mansion (except for Constance who has the aforementioned problem of using a flat 2-dimensional facial surface) look quite good. The attraction lighting is EXTREMELY dark already, so conflicting show lighting is minimized and results in projections looking sharp and clean. Most of them (the classic effects of Leota and the busts) are also just heads anyways, so it helps that they didn't have to light a surrounding body. The glow of the projections also fit much better due to the ethereal ghostly nature of the ride.
