A theory is no longer a theory when it becomes a fact or is discarded.Scientific theories are facts assembled into reasonable pictures. The Theory of Gravity uses the facts about gravity to produce the most comprehensive picture that can be formulated.
.It reminds me of what Dr Isaac Asimov said. A theory is not wrong it just needs updating'.
Like the theory that there was nothing, just a vacuum, in outer space. This theory was totally discarded when it was found that there were magnetic and other fields unseen by humans.