Vacuums exist. Nearly frictionless planes and more or less perfectly rigid bodies actually exist. There is nothing wrong with abstraction based on objective reality. Claiming that one is about to declare how economies ought to work is not a abstraction based on a preexisting reality. It is attempting to impose one's own subjective needs wants and desires on reality.

That is not science, that is pseudoscience.

Spherical cow is not "how science is done". It is a joke. Jokes rely on reversing expectations, going counter to reality, for the surprise element. How science is actually done is you begin with the intent to describe the real world and from there you use whatever tools, intellectual or actual, at your disposal in order to accomplish your goal.

If one's goal is not to describe how economies actually work you are not doing science. Declaring what one's ideal economy ought to be is not the same as describing how a real economy would behave under ideal conditions. If I declare how photosynthesis ought to work I am not doing the same thing as describing how photosynthesis actually works under ideal conditions. It seems like a subtle distinction but it is not and failing to understand this difference has lead to a lot of bad science by lesser minds.

Suppose a man goes to the supermarket with a shopping list given him by his wife on which are written the words "beans, butter, bacon and bread". Suppose as he goes around with his shopping cart selecting these items, he is followed by a detective who writes down everything he takes. As they emerge from the store both the shopper and the detective will have identical lists. But the function of the lists is quite different. In the case of the shopper's list the purpose of the list is, so to speak, to get the world to match the words; the man is supposed to make his actions fit the list. In the case of the detective, the purpose of the list is to make the words match the world; the man is supposed to make the list fit the actions of the shopper. This can be further demonstrated by observing the role of "mistake" in the two cases. If the detective gets home and suddenly realizes that the man bought pork chops instead of bacon, he can simply erase the word "bacon" and write "pork chops". But if the shopper gets home and his wife points out that he has bought pork chops when he should have bought bacon he cannot correct the mistake by erasing "bacon" from the list and writing "pork chops".

Scientists are detectives attempting to describe how the world behaves. If the world behaves differently than we expect we erase bacon and write down pork chops even if we really would prefer bacon. Idealists, fantasists and Austrian school economists want bacon on the detective's list so they write down bacon and blame reality for not living up to their desires.

That's religion, not science.