Why the Night Sky Is Dark

Don't you think theoretical physicists have gone too much creative and radical in the past few decades? For instance, we are talking about multiverses, parallel universes, higher dimensions, holographic principles. They don't have any experimental grounds. We can only observe what exists in the observable universe. And beyond the universe, if there is something beyond, there is no way of knowing what's out there. Any scientific theory needs to be a testable and b, falsifiable. It has to be science.