I fully agree with you. Constructive criticism is needed if people ever hope to improve, with fandom projects or otherwise, because it's not possible to spot all errors on your own. No matter how much I study writing, it's the feedback I get from others that really makes me want to take it a step further. Too bad not everyone is open to critical feedback and will lash out at you at the slightest thing negative in a comment, even if it is just to be helpful.