Why is stating that only the Sun's gravity binds the system together considered an oversimplification?

Answer

The solar system is a complex N-body system where every mass influences every other mass.

The system is modeled as an N-body system, meaning that while the Sun is dominant, the cumulative gravitational influence of all other masses affects the long-term stability and positions of bodies.

Why is stating that only the Sun's gravity binds the system together considered an oversimplification?
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