That all sounds very idealistic, dare I say naive.
People do not typically assess their own happiness by looking at those less fortunate than themselves. They may feel a sense of relief that their situation isn’t as severe but that is not happiness.
Human beings fall ill and pass on, every day. Those are guaranteed outcomes. So yes, while we may all have unique challenges that we’re all made to face there are some core facets to the human experience that none of us can escape. People who suggest that happiness is anything but fleeting and impermanent are deluding themselves.
The human experience itself is fragile and unpredictable. How then can human happiness not be?