Science derives its legitimacy from grounding in what anyone, anywhere can observe. It's called "empiricism." But the very success of science has tempted people in all fields to promote theoretical ideas before there is appropriate empirical support.
String theory had its origins in 1968, and over 50 years it has become the darling of theoretical physicists as a candidate for a Theory Of Everything. Thousands of scientific papers have been written about string theory, because the mathematics is so much fun and leads to so many interesting places. But the acknowledged drawback of string theory is that it has so many different forms that it you have to write an exponent within an exponent to write the number. Hence, there are no predictions from string theory, and no way to test it against the reality of our world.
This spring, finally a general prediction was derived, true of all string theories. Dark energy must decrease as the universe expands. But in our universe, dark energy seems to be holding steady.
String theorists are not taking this sitting down, but are applying their creative energies to the discovery of loopholes and exceptions.