I think there is a point you have to set boundaries. If people criticize your work, maybe you aren't the artist for them(not meant with malice). Sure, you might like the work but sometimes you have to protect yourself. Your portfolio will tell others what to expect. Unless you deliver something WAY off, and/or that is quite different from what previous work you have done, then you are providing what they were apparently looking for.
I managed this very well in photography business but it took rejecting a lot of people, and their unreasonable expectations, before they were able to show dissatisfaction.
As for the wing, I'm not sure what he asked for but the font isn't my favorite(that's just me and maybe what he wants). The wings are perfectly within the variances seen IMO. A line of heavy stitching around it and a little wear and they would look great!
It sounds as if his criticism isn't based on anything but conceptions he has developed and you might never be able to hit that magic image he has. He should give you something to copy if he has a specific idea.
Keep posting the great work!
Dave