On the one hand, talking with people about your anger can be useful and positive. It can give you some perspective, help you process what you are feeling and better understand your emotions, and even offer an avenue to receive some constructive criticism regarding how you handled a situation.
That said, that’s only true if you are looking for perspective, understanding, and constructive criticism. Most people aren’t. Most people are just looking for another person to agree with them that they should be angry. That’s ok every now and then but too much of it isn’t good for you. If you want to rant every now and then, go for it. But make sure you do some self-reflecting at the same time.