It seems there might be some confusion about the scientific meaning of the word "theory." In scientific terms, a theory is not just a guess or an assumption. It's a well-substantiated explanation that has been supported by extensive evidence and has stood up to rigorous testing and scrutiny.
Gravity is indeed described by the scientific theory of gravity, which is based on the work of Sir Isaac Newton and later expanded upon by Albert Einstein's theory of general relativity. The theory of gravity provides a framework to understand and predict the behavior of objects in the presence of mass.
When people cite gravity as the reason objects fall down toward Earth, they are referring to the well-established and extensively tested understanding of gravity provided by the scientific theory. The theory of gravity has been consistently supported by numerous experiments and observations, and it has allowed scientists to make accurate predictions about the motion of celestial bodies, the behavior of objects on Earth, and even phenomena like gravitational waves.
While science is always open to new evidence and ideas, the theory of gravity is considered one of the most well-supported and fundamental theories in physics. Its predictions have been confirmed countless times, and it is widely accepted as the most accurate description of the force that governs the interaction of objects with mass.