There are absolutely academic economists who are doing a reasonable job trying to find the objective truth underlying human behaviour in economic life, understanding market forces, understanding relevant institutions, and so on.
However, the majority of what actually makes it into the public discourse is simply politically motivated reasoning, often in the form of hacks writing for think tanks that are paid for by special interests.
It's amazing to me that, at least when I was at university, the computer science curriculum had more content concerning ethics and our responsibility towards society than the economics curriculum.
No other field of knowledge is as poisoned by politics as economics, by far. That's why even though economics can be a decent science, a healthy amount of scepticism towards anything you read by (even supposedly academic) economists in the public discourse should be the default attitude.
"Many empirical controversies in economics are essentially disputes about whether or not certain variables constitute valid instruments" - Econometric Theory and Methods, Davidson & MacKinnon
Pretty broad statement. Some micro-economic theories, like the game theoretic models in auction theory, contract theory, mechanism design and behavioral economics are probably the most successful, accurate and impactful theories in all of social sciences, including psychology.
You may not realize how much your buying behavior, your salary, your interactions online and your use of technology are dependent on these models. But comparing their success and use to fields like sociology, management and even psychology, their track record is frankly amazing.
We already know that Macroeconomics amounts to modeling systems that do not aggregate meaningfully from these successful micro-models.
Saying economics is not a science based on this, is like saying physics is not a science because we still can not find a unified theory. Which is a pretty good analogy for a Macroeconomic model that forecasts GDP (aka, everything).
You've never looked at a macroeconomics model, have you?
Economics is complicated because it is modeling the behavior of human beings.
Math is easy, computer science is easy, modeling the collective behavior of humans is hard.
But macroeconomics is indeed based on a lot of things, and you seem to be very misinformed. Macroeconomics relies very heavily on mathematical tools such as calculus and topology to model the collective behavior of humans.
If you are really interested in learning more, I recommend "Knowledge and the Wealth of Nations: A Story of Economic Discovery".
Nobody derived Navier-Stokes equations to reach the formulas that show the erosion of a river bank, or the discharge calculation of a weir. Doing so would be nearly impossible given the extremely high level of complexity.
So instead of trying to start with the fundamental equations and build "up", you start by analyzing the behavior and modeling it.
It isn't any different than what Kepler, Newton, Galileo, etc. did: you look at the real world and build models that describe the world with enough precision for what you need.
Sure, you might say that hydraulics isn't a science per-se, but an applied field and so on. In that case, so is economics.