I'm sure you can think of some things, but as long as it agrees with the available evidence and is the "best explanation", which includes some subjective and objective criteria, it's a valuable theory.

You specifically mention Popper. Poppers criteria of falsification states that it is not enough that a theory can explain everything. He observed that a lot of pseudoscience (astrology, marxism, freudian psychology at the time) really could be used to explain everything and couldn't really be disproved by any observation. Real scientific theories on the other hand could be used to make predictions which could be verified or shown to be wrong.

I mentioned Popper because of his emphasis on good explanations. It’s a lot more than falsifiability.