You are using an incorrect definition of the word. Theory used in science[0] means:
a coherent group of tested general propositions, commonly regarded as correct, that can be used as principles of explanation and prediction for a class of phenomena
and not:
a proposed explanation whose status is still conjectural and subject to experimentation, in contrast to well-established propositions that are regarded as reporting matters of actual fact
We have a separate word for the latter: a hypothesis.
a coherent group of tested general propositions, commonly regarded as correct, that can be used as principles of explanation and prediction for a class of phenomena
and not:
a proposed explanation whose status is still conjectural and subject to experimentation, in contrast to well-established propositions that are regarded as reporting matters of actual fact
We have a separate word for the latter: a hypothesis.
[0]:https://en.wikipedia.org/wiki/Scientific_theory