Complexity in the sense discussed is related to the domain knowledge (including CS knowledge) required for the program to be written and work well.
Else even a trivial BS program could be very complex, just sprinkle it with gotos and unnecessarily convoluted code...
Simple programs which are coded simply may address complex phenomena to complex ends--perhaps that's even the ideal?
I don't think this is true. For example, as a math teacher, I couldn't do a very good job predicting how easy or difficult students would find particular problems. But I could easily predict which problems would be easier and which would be more difficult. I could do that even though I personally understood all the problems.
I'll attribute difficulty to the energy required to resolve a system. For example, pulling weight. The complexity of the action is the same. But the difficulty depends on the weights to pull.
Complex rules yields stupid results. Example: tax codes in most countries.
Must be a quote but I wasn't able to find a source for it.
When systems get too complex to simulate from first principles, we have to resort to inductive reasoning--observe the system and then create rules as we see a need.
Yes the resulting rule set is a mess, like our tax code. But the physical system that the U.S. federal tax code (for example) covers--the United States of America--is mind-bogglingly complex.
We have trouble computationally simulating more than a certain number of neurons... there are billions of neurons in each human brain, and there are hundreds of millions of human brains interacting in the U.S. This does not even get into other physical phenomena like surface water or mineral distribution.
The results are stupid because we are too stupid to understand and analyze the system we're trying to describe and manage.
Back when I was in academia I used to develop ABMs to represent the behaviour of complex systems with a simple set of rules of agent action and interaction.
The game of Life is the quintessential example of that.
For instance, the payload which specifically looks for uranium centrifuge hardware is independent of the worm which carries the payload. They can be developed separately, by different people, and combined.
That specific worm could carry a payload to attack anything.
Or, that specific payload could be carried by any worm.
There is next to no coupling between "worm" and "payload".