Theory and evidence go together. Either one absent the other is pretty useless.
Perhaps I misunderstand. Not sure what you're saying, but ponder this: If theory is assumed correct, but there is no empirical evidence to back it up, I agree that the theory was not directly helpful. (Indirectly the theory can still be useful. It isn't possible to prove every theory correct [theorem?]). Conversely, however, if practice and use reveals that something works, why does it matter what the theory says? That part does not make sense to me. If it works, it works!
"Often moments come looking for us". - Robert Frank
"Make good art!" - Neil Gaiman
"...the heart and mind are the true lens of the camera". - Yousuf Karsh