I think the thing that pisses me off most about “constructive criticism” and all the people insisting that they have the right to give it, is that people don’t actually do it correctly for the media they’re consuming. Like, as soon as they see it’s allowed (or even regardless of whether people want it) they just... shit all over the piece of work.
Listen. This is a hobby. People do this for fun. A reader is a peer, not someone who is above them--they are not an editor or an agent. You know how you critique as a peer? You make ‘I’ statements and offer explanation. If you find a huge problem, your fix is a specific suggestion. You make it clear that it is you, the viewer, having the problem, not the author, and you offer reasons so that they can apply it next time. And, above all, YOU ARE RESPECTFUL ABOUT IT.
“You made [Character] so out of character!” strikes much differently than “I found [character] to be out of character because of x, y, and z.”
“Your writing style is blocky and hard to read.” strikes much differently than “I struggled with the large blocks of text in this. I think it could stand a couple more paragraph breaks.”
“You tried to do something new and it sucks.” strikes much differently than “I see you’ve tried something new and am glad to witness you trying to branch out. I’m not entirely sure it was successful, but it was a pleasure to see you taking the chance to grow your skills.”
I have kept this ‘I statements’ technique in mind all of my thirty years and it has never once steered me wrong. One of my writing teachers in college even mentioned how diplomatic I was and how receptive the other students were to my suggestions.
Of course, this is all in the case that constructive criticism is welcomed. If there’s no indication whether or not it’s welcome, you have to fucking ask before you throw it into their inbox, and you have to respect when they say no. In that case, if you can’t say anything nice, don’t say anything at all.