I hope you don't mind, Caesius, but I went through your pictures and outlined the shape in both comparisons, in hopes that it will show clearer what the issue is.
And I also want to say in advance, it's very, very clear how much the textures improved, and the details do look incredible. It's clear the Dev team is putting a lot of work into this, and this comment is not meant to undermine that. But to help address why people still feel like something is "Off" and different about their characters.
Lips give a lot of personality to the face, and their shapes have clearly been altered and modified.
I apologize in advance that this got large.
Now, I've been noticing two main things in how the lips where changed:
The lips have all been extended to the very corners of the mouth. Which is something that does not always happen, not to mention it changes the expression of the face.
The most clear examples are Male Viera, Miqo'te, and Elezen, but that is noticeable on most faces.
Here, with the outline on the picture itself, you can see how the lips now extend to the very corner of the mouth, altering the original shape.
Though that is far from the only issue. Some cases the lip shape was altered almost completely.
The Female Au Ra is an example of how the lip is now much more Full, rounded, and heart shaped.
Honestly, looking through all of them, what saddens me the most is how the shapes have become generic, and uninteresting. They have lost almost all, if not all, of their uniqueness, and personality. Especially in the Female Models, they look very generic, doll-like, and standardized, though the same is true across all faces.
It does feel a bit like they got a little "Over-Zealous" rounding out the shapes, and in turn, losing much of their uniqueness.
I do hope this helps showcase the issue people are having and how the shape itself has been altered, and why people are upset over it.