There can be many reasons for "why your girlfriend never appreciates you"?
You don't deserve a comment.
You always criticize her and never appreciate her. You get back in life what you give to others. Law of life 😄😄
You are above such trivial things and does not brag for appreciation for petty things.
You might have given her the vibes that you don't need any appreciations and you are cool.
She knows that you will not leave her even if she does not show any love or interest in you.
This reason may break your heart but 99 times out of 100, this will be the correct reason.
"She does not care for you anymore. She is done with you, and found someone else."
It's better you move on with your life!!