some moral laws will seem to limit human pleasure in the short term, but will prevent great suffering or maximize happiness and fulfillment in the long term

Well of course. Memetic natural selection ensures that only those cultural values which promote the long-term resilience of their cultures survive long enough to become recognized as "moral laws"; cultures which fail don't transmit their values to the next generation. So when we're looking at any traditional value, we should be doing so with conscious awareness that that value was an element of a culture which survived long enough to become traditional, and we should be very hesitant to replace it with a novel and untested alternative. The vast majority of mutations are either trivial or fatal, and this is just as true culturally as it is genetically.