As I have often said, there is no useful general definition of happiness. Unhappiness and misery are much more easily defined.
Do all people need a sense of mission or purpose to be "happy" - other than the basic mission of survival and comfort? I very much doubt it. The wonderful psychiatrist Victor Frankl was indeed sustained by his search for meaning in the camps, but that is far from ordinary life and he was far from an ordinary man.
Here's Emily Esfahani Smith's There's More to Life Than Being Happy. I am not sure what I think about that report.
For me, contentment is a good, loyal husband, a good love life, good work, enjoyable if sometimes difficult kids, good friends and good acquaintances, exciting hobbies and sports, integrity and a clean conscience, a dog, a relationship with God, and books to read. Changing the world is a fool's errand for crazy people and narcissists who do not want to focus on the substance of their own brief lives. Can't do without them, though. Part of the fabric.