Feynman believed that it is unlikely to unify the four fundamental forces (strong, weak, electromagnetic, and gravitational) completely within a single formula or theory.

I agree with Feynman’s view.

Unification of the Four Forces: Unity at the Level of Principles, Not Formulas

True unification of the four fundamental forces does not mean forcing them into one long, patchwork formula. Pursuing a single formula by force is like cutting fingers of different lengths to the same size — it looks neat, but it actually violates the nature of reality.

A more reasonable direction closer to physical truth is unification at the fundamental principle level.

The four forces may share a common origin in underlying logic: the same set of symmetries, gauge structures, spacetime roots, and conservation law mechanisms. They emerged from the same source in the early universe, but as energy decreased and symmetries broke, they gradually evolved into four distinct forces with vastly different behaviors, strengths, and ranges of interaction.

They do not need to share a single line of formula; each can have its own concise and clear expression.
Yet at the level of fundamental principles and physical foundations, they belong to one unified framework of understanding the world.