I do not really complain a lot, as I am a type of person to keep stuff to themselves. I do think complaining and letting it out can be healthy coping mechanism though, as long as it is justified and not someone making drama over every single thing. Some people use complaining as a way of emotional abusing and forcing others into what they want. I quickly cut ties with anyone who uses complaining to manipulate others.
There are a lot of people - especially in older generations - who see complaining as sign of weakness. However, it is important to communicate your feelings, especially if something or someone is making you really uncomfortable.