For example, saying things like "you're so bad", "holy expletive what was that horrible x", "why can't you x", mocking someone for a play(this one is a very popular one), or just flat out flaming people are not good criticisms. They're all unhelpful in their own separate ways, but one thing they all have in common is that they give 0 helpful information to the person other than you're displeased with them.

Instead, try to actually tell people what you think they should be doing, and make sure you word it in a manner that isn't hostile. Not only will it help convey actual helpful information, it will be more likely to actually be considered by the person you're giving the advice/criticism to.