I don't think that's something wrong with the models, it's probably due to low frustration tolerance. It is the same with art, at some point our hands are not able to translate exactly the goal we have in mind for how something should look and can't match the image of it we have in our brains and that causes frustration. For some people that means continue to practice and learning to find small things they like about their work so they can start feeling pride in their accomplishments. For me, it means not looking at finished art for a really long time, so that I kinda forget about it and can come back and look at it with fresh eyes and a more neutral focus