This study revisits the value of Bohr's theory, and uncovers its semi-classical research philosophy—one that pursues bold innovation in tackling complex problems, unconstrained by existing frameworks or theoretical rigor. Inheriting this idea, we ingeniously apply Bohr's theory to calculate the energy of multi-electron atoms, obtaining results consistent with experimental data, thereby epitomizing the strength of a simple physical model and manifesting the value of the semi-classical research philosophy.