You mixed up - I hope intentionally - two different things. Understanding is frequently a back of the envelope thing. Example: E=MCsquare. Profound, lesser understandings flow from it.

On the other hand a simulator, any simulator is iust a tool. Well built, or badly built. It is useful in skilled hand, worthless without understanding. It saves labor.

Recently, I tutored a fellow in selecting the right sensor for a feedback loop. His simulator program did show good response. His actual application did not work. I looked at the manufacturer's spec, and the sensor had no specified response at that frequency. Did he listen? No. He chose to believe the simulator. Amazing!!

I will take this opportunity to post a link to a classic piece of software developed right here

thanks to tcmtech

Having Bob Pease, Williams and Gilbert among the main stars of my engineering firmament (starry landscape in latin) I am saddened by the passing of the first two. It is appropriate to borrow one profound statement:

Simulation, what it is worth

Best regards