Something that I’ve noticed happening over and over again is a new user showing up with a homebrew piece of game content (e.g. a race, class, feat, et cetera), and then posting a Question to the effect of “Is my thing balanced” which almost always has an Answer of “No, it isn’t.”
It’s to the point where I’m considering posting a Question of my own that’s a generic version of the question with a self-Answer of “No, it probably isn’t’” with an explanation of why that’s likely the case (professional game designers do it for a living and have more experience, their designs often include hidden assumptions about how things are structured, they sometimes utilise community feedback cycles to test things, etc).
That way whenever one of these questions get asked, we can just link to the general case in the Comments. I think that they’re called a Community Wiki entry?