These are intelligence agencies. Being secretive about what they do is largely the point. Some degree of oversight is of course required to ensure that the organizations haven’t been subverted and are still on-mission, but the responsibilities of an intelligence agency are too fragile and too essential to be subjected to political meddling.
"Blindly trust us, or bad things will happen" has no place in a Free society - especially after they've been repeatedly caught abusing that trust. There are many steps NSA could take to increase their transparency without exposing the details of operations, but as I said the problem is that they actively oppose oversight. This is likely due to the usual authoritarian delusion ("taking more power will help accomplish our benevolent goal"), which is at odds with democracy.
