Agreed that affirmative happiness is very hard to think about as a target.
But I find that most people, when they say that, actually mean reduction of suffering. That's easier to quantify--but still quite difficult, like most quantities in social research.
Do you not then run into other problems? For instance I find that lifting brings an immense amount of contentedness, yet it's essentially hours upon hours of self inflicted suffering and pain. The same is true of family. Somebody raising a 2 year old could describe it in many ways, but reduction of suffering would not be one. Such things greatly contribute to this sense of contentedness and satisfaction.
But I find that most people, when they say that, actually mean reduction of suffering. That's easier to quantify--but still quite difficult, like most quantities in social research.