Trick question since I believe I already know the answer. But I'd like to hear some other views.
I believe that Economic Theory is like Psychology, it pretends to be a science, when really it is a religion.
People base their opinions on their beliefs. There usually isn't enough facts to go on, anyway.
A basic definition of what I mean:
Integrated Economy would be what the EU is aiming for. Seamless easy access for business to span borders. Favours big business.
Isolated Economy would be North America up to the 80s. Tariffs on most things to encourage local sustainability. Favours small business.
Integrated, total output is maximized when economies concentrate on areas of comparative advantage/expertise producing more at lower resource cost. However a symptom of this is competitiveness which means constant innovation, which as a whole is generally better for the world (more cheaper output increases total wealth and fuels real wage growth) however individual populations will suffer when their skillsets become irrelevant (i.e. the argument of Luddite movement).
Economics is often referred to as "the dismal science" as it is heavily observational (like most social sciences), basic economics principles translate universally; they can be applied in areas like physics (most energy related topics also follow economic principles) to biology (biology is all about resources and their transfer). Other economic principles can range from being as dismal as sociology (limited in scope and poorly observed with weak/no design of experiment, sometimes even just made up) to huffpost caliber clickbait (there are some pretty easy tells to identify total bullshit).