Everyone has things to complain about—if they choose to—that's life. You are almost guaranteed to experience daily inconvenience, unfairness, and people doing things you don't want them to do.
Complaining is a bad idea. As an action, it's even worse.
Let's use two examples:
If you were given the job to coach someone and your compensation was based on her performance, in what situations would you advise her to complain to colleagues and get defensive when people challenged her approach?
If you advised a man having trouble in his marriage, when would you explain, "Blame your wife for the problems and complain to your friends for the next couple years. That will lower your stress and improve the situation."
You wouldn't give that advice, not if you cared about the person and not if your income was tied to their success.
Complaining feels justified, and therefore productive in the moment. It may be justified but it isn't productive.
What should you do instead of complain?