But you have been alive for what, 20 years? That gives you the experience to state what you like, and possibly more importantly what areas of a picture you do not like. Assuming that you are not blind, you have been looking at things for quite some time. That is an invaluable experience, being able to say whether an image looks 'right' to you. Don't know who said it, but there is a famous quote, "I don't know much about art, but I know what I like".
If you state what you like/dislike about a finished image, without prejudice about how the image was created, because after-all, the image is the reproduction of the pixels/molecules to produce light, not the method of how it was done, then anyone who claims that you do not have experience, and thus your view is unentitled, is being short-sighted.
This is the only semi-valid point I think. If you do not feel that you have taken enough pictures, to be able to say technically how you think a shot should be re-taken to be improved, then that is your choice. Technique on processing and taking a shot is something that comes down to having done it more than once (otherwise it is a lucky first-time guess).
I think that everyone on here who is capable of seeing an image, is allowed to have their view on whether they like an image.
No matter how many shots someone might have taken in the past, or how 'respected' they may be in their field, you have the right not to like their image.
How you express that right is down to the individual, it needs to be polite. Personally, I say that an image does nothing for me. I tend to not leave critique on images which I find a mediocre to me, and that others have already commented on, /when I cannot clarify why it does nothing for me/. If I like part of an image, but do not like another part, then I try to say why. It doesn't matter how many times that person has done it before, if you can say why you don't like something, so long as it is in the 95% percentile of views, then by taking it on board the original poster can perhaps remove that from their next shot, and have more people like it overall.