If asked for, constructive criticism helps the learner grow. Constructive means you don't ridicule and chide. Instead, you tell them exactly how to fix what you think could be improved.
Those who make unconstructive and hurtful comments are holding themselves back. If you waste your time making fun of others and only focusing on what you deem as "bad" you do not grow as an artist.
The best way to grow is to look at images that you think are amazing, then ask yourself:
What is it about this image that caught my attention?
Do I like the lighting? If so, study it and try to take that element into a theme of your own. Try to recreate that lighting.
Do I like the pose? If so, what is it that you like about the pose? Go forward in your work using the things you like in future poses.
Do I like the wardrobe/styling? What do I like about the styling?
Do I like the hair/makeup? What do I like about the hair/makeup?
Do I like the post processing? What about the retouching do I like? Then research how to retouch in such a way, taking elements of the retouch and adding your own twist to create you own style.
Do you like the feeling, location, etc? I think you are getting the point by now.
It is important that you do not replicate everything in an image. That is stealing. It is copyright infringement. What you do is pay close attention to the things you like, then incorporate those elements into you very own concept.
By looking at all these elements and learning them, you are learning to improve. When you sit back and become and armchair critic, you hold yourself back. You do not look at what you can do to improve your own work, you just wallow in what you think is bad. It is a quagmire that you will get sucked into if you are not careful.