What an utterly absurd question. You've clearly lost sight of what's important: The metrics.

Yeah the islanders might say they are happy but are they meeting or exceeding their OKRs?

More importantly, how much did their 401k grow last year?

It’s easy for a society to be “happy” (whatever that mean and however you measure that) when only fully healthy people get a chance to live and everyone else is dead.

Are more people individually less happy better than fewer people individually more happy? Do you just multiply the two together to decide which is morally better?

More importantly, do you factor in people died from otherwise treatable diseases as negative happiness, or neutral (as they no more have a brain to secrete serotonin)? Is death unhappiness? For the subject and his relatives? When death is commonplace is it still a source of unhappiness or accepted as a part of natural flow, with human life being regarded as less permanent and more ephemeral, with greater emphasis on the present moment and less on future plans and ambitions?

Death is commonplace everywhere. Everybody dies.

I actually don’t think that’s too relevant of a question. If there’s a high amount of suffering and cruelty, along with a mental philosophy that allows for happiness in spite of that (for the survivors), that still doesn’t make the suffering ok. To say otherwise is to take a step toward justifying slavery if the slaves are conditioned to be happy…