people think economics is a science but it doesn’t consider human nature

That’s literally the whole field of behavioral economics.

Also, economists don’t care about individual human behavior. That’s not what economics is. Economics is the study of broad trends in large populations. And for the most part, modeling these trends as people trying to maximize their own utility function is a useful tool to explain things.

Also also, the point of science is to be measureable and falsifiable so that hypotheses can be tested and disproven, making the predictions of the field more accurate over time. Economists create falsifiable hypotheses. Often they are disproven. Economics gets better at modelling the real world over time. Economics is a science.