First, I really appreciate author trying to understand economy better in this way, even though this simulation is quite naive. I think everybody should do that. But as others have noted, it has no concept of capital, private property, and labor market. Therefore, it's not capitalism. It's not anarchism or communism either - it lacks flexibility of workers to do something else, or state planning telling workers to do…
Would rich people be able to stop you from creating a good economy simulator? At the end of the day, it's programming. Someone who has studied economics could make that without rich people coming after him. I argue that no one would come after you if you were to do so.
So you need to understand the real-world monetary flows to a sufficient level of detail. You need to understand who actually owns what, and how the power is exerted. And the rich people are against that, for example, in most developed countries (with IIRC notable exception of Norway and Sweden) the tax fillings are private.
Also, it's kind of difficult to understand actual production, because private companies keep the data on production costs secret.
On top of that, there is little culture of data sharing in economics profession. Again, mostly because the data are very valuable to companies and individuals, profit takes precedence to public understanding.
So the fact of the matter is, lot of powerful people (and perhaps most middle class as well) don't want the level of transparency required to build a meaningful model.
It's true that nobody will come after you if you try to program it. But also, you won't get much support from the existing, mostly neoliberal, institutions.