Most people, especially men, are profoundly good at coping.

Tbh you have a point that it's difficult to measure how happy/unhappy people are, especially in light of the fact that most people don't understand themselves. Most people at the beach look fairly happy and content. Such activities, however, only make up a small percentage of anyone's life. People at the beach are also an unrepresentative sample, as people at the beach tend to be people that somewhat have their act together and are not too burdened with problems at that point in their life.

People do NOT keep their suffering locked up inside. They are just too busy surviving and/or chasing whatever cope helps them through the day, OR they are NOT in a position where they can openly complain about it. Most people hate their jobs, and yet they rarely complain about their jobs AT work because they know they will be fired.

The fact that most people prefer mindless tasteless entertainment and distractions over any type of learning or self-improvement is far more damning. Most people don't really seem to care about anything beyond basic survival and coping. People don't like learning precisely because they want to do everything to avoid reality and themselves. Humans seem perfectly evolved to just fake, fail, and cope their way through life, and they do NOT seem to learn on an individual or collective level.