For some reason, I never noticed the supposedly quality difference in the 3D models.
For Myth, there was Calli's flat face, but that was fixed relatively quickly?
Ame's model also frequently came out when people talk about poor quality 3D model, but you need to consider the fact that most of the time when we see her 3D model, it was mocapped using Ame's own studio, which is more scuffed than an actual studio. There's also the complaint about her inner-coat sticking to her body, but I can understand why they do that, try to imagine how the coat's physics would be like if it is a separate layer, especially when she is bending or sitting down, it will probably be a mess. I'm trying to think if there are any Hololive talents wearing similar coat as Ame, but got nothing, so I can't even compare.
Tldr: Ame's design is probably hard to translate to 3D model since it has too many layers.