I think studying well defined and important things is... extremely important :) I think for example it should be possible to measure remission from depression.
I also think though that psychology could 'make philosophy out of its physics' (in an analogy with an experimental field like chemistry or material science), and form theories about happiness, well being, etc.. that are grounded in insightful philosophies. And then try to measure or make some progress and recommendations to guide the field (like, how should we define well being, how should we measure it, and what kind of interventions help it).