Flagger said:

hideous 3D hair

The plastic-like hair is a design choice by the artist since these 3D models are actually meant to be made into figurines:

Rasetsu Hime Suna Oni 3D model by LESLyzerosix
Prototype figurine seen at WF2018 Winter

Musashino Takumi 3D model by LESLyzerosix
Actual figurine released last month

All of LESLyzerosix's models on Danbooru exhibit this trait. This is because artist creates these models in a program called ZBrush.
Due to the Pixol technology utilized in ZBrush, the hair will always look like fused dough. The whole point of the program is to digitally sculpt models that can be potentially realized into physically tangible figurines. Thus, the fine strand granularity and sharp definition of hair that can be achieved in 3D modelling is not suitable here; the end result would be too frail for anything practical.

The hair is not a flaw, nor does it look out of place when you consider the context and purpose of digital sculptures.

Flagger said:

thigh gap you could run a train through

This may also the first time in Danbooru history for an image to be flagged for having a thigh gap.
However, there is nothing wrong with the size of the thigh gap here, in fact it may be one of the most realistic aspects of this model.
Compare the gap on this model to what we see here in the following examples (Warning: Questionable rating)
Danbooru exhibit A
Danbooru exhibit B
Danbooru exhibit C
Danbooru exhibit D
Danbooru exhibit E
Real life example

The thigh gap that we see here doesn't even approach the realms of grotesquely wide.
An actual thigh gap that could fit a metaphorical train would look like this (Warning: Eye bleach recommended)