You are confusing between useful systems vs explainable systems vs understandable systems. All models, 1:1 or not are useful in some sense. You might also be ab

You are confusing between useful systems vs explainable systems vs understandable systems. All models, 1:1 or not are useful in some sense. You might also be able to explain some event or behaviour of the system using a model. However, understanding requires building abstractions graph that can allow an arbitrary chain of reasoning and inference. As system becomes complex, such abstraction graph might result in similar complexity resulting in inability of a human to store in memory and execute inference/reasoning over it.