Doesn't that almost imply the happiest countries in the world have a lack of imagination on what could be better? Or maybe they don't suffer from comparison (the thief of joy) as a culture.

>a lack of imagination on what could be better

I'd argue it's likelier that people are more informed about their absolute position globally. Any screen gets you the mental image of the top of the ladder. So happy people would end up scoring themselves low, because there's a globalized vision of wealth nowadays.

Besides there's a difference in life self-evaluation and experienced happiness, so the report really is a misnomer.