I think what people are misunderstanding when I say suffering must exist in order for happiness to exist, is that they think I am referring to specific individuals. I believe if anyone experienced happiness, in some way, it is likely at the expense of oneself or another. For example, if you like icecream, you can buy some, and that can make you happy, but someone has to work a shit job at a store that sells icecream in order for you to buy it, let alone all the people who had to spend time and work in a miserable environment making that product.
While a world without suffering is a good ideal, I personally think it is impossible. To exist in a world where no one suffers, is to exist in a world where everyone's views and feelings are homogenized. If anyone has any disagreements, there will always be some level of discomfort. And I think feeling unpleasant things is what drives us to improve, and to learn and discover more. If everyone was happy, we would cease to move forward, cease to make art or invent anything new, because there'd be no motive to.
That's just my 2 cents. Thanks for the positive feedback!