Now you just know I'm gonna critique definitions here.. :)
I think you mean hypothesis in this case. In science a theory is closer to a law - the main difference being that theory is usually more complex, involving more factors (or laws).
A theory explains related observations, is based upon a proven hypothesis and has been verified or repeated by multiple researchers. Both theories and laws are accepted as true, used to predict events, advance new technology, etc.
Einstein's Theory of Relativity be an example. It was "proven" true by experiment and prediction. Newton's laws of motion still hold for certain frames of reference but at high speeds Special Relativity must be taken into account for accuracy.Newton's are still called Laws.
It may be that E=MC2 is supplanted by another "theory" which is more accurate, but, if this occurs, likely it will become like Newton's, accurate except for.. IOW, still true or works, but..
Anyway "theory" is not a pejorative term for science; hypothesis or "one man's hypothesis" would be.
Well, yes, theory in science is supported by observational/measured data; it is a working model. But it is not the same as uncontested fact.
Ptolemy's navigational system is a working model, which works fine even today, but is completely flawed as far as the solar system and planetary motions are concerned.
So, just because observational data "confirm" the hypothesis doesn't mean the world is how the working model describes it!
Also, its inherent incompatibility with Quantum mechanics suggests that either or both models are seriously flawed.
Both working models are based on postulates which have yet to be conclusively proven. At this time, there are new discoveries that seriously challenge these gold-standards of the late 20th century cosmology.