You are mistaking "theories" and "hypotheses". Theory in science is not some wild shot in the dark, imagined by some random guy in the eureka moment. And neither it is a something yet unproven. Theories in sciences are usually sufficiently proven and stand on the other previously proven theories. Like for example evolution of species is a theory, despite it having more than a century of research and hard proofs. So yeah, science is based on theories, but not on a collection of lucky guesses.

Now hypothesis is what you were probably mistaking a theory with. A hypothesis is something unproven and may or may not be a real thing.

I did mistaken those, thank you for pointing that out. My point remains that science operates in the real world, where decisions often have to be made based on incomplete evidence, rather than waiting for certainty.