I fundamentally disagree. For most people, being happy is not a state of constant bliss without any concern for anything else. They are content with a life that has less negative experiences than positive ones, and I'm 100% sure that they are the majority.
My claims are based on what people tell me, my friend. They are all brunch of optmistic pro-lifers who tell me they are happy, then they start complaining about work, life, government, society and they even say really dark shits like "humanity is a plague" and "meteor is a hope". I'm not deciding what they consider happy or unhappy - they told me. The only thing I'm deciding here is lack of consistency in saying that they are happy when they hate most of the time on their life.
Complaining doesn't necessarily mean being unhappy with the entirety of your life. I've met plenty of people who say similar stuff and I'd say that they live in a relatively complacent but overall happy state of mind, of course people hide a lot of stuff, but that's no reason to asume that everyone is hiding discontent or straight up suicidality.
In a similar fashion, I can say that I just had a really good cup of coffee, doesn't mean I'm happy with my life.
I think you are seeing things in black and white, which is understandable, but don't take any single negative aspect of other people's lives and asume that they are not having happy lives.