The first "secret" to good production audio is proximity, getting the mic in close.
In physics, an inverse-square law is any physical law stating that a specified physical quantity or intensity is inversely proportional to the square of the distance from the source of that physical quantity.
So a mic four (4) feet away is only one-sixteenth (1/16) as loud than a mic one (1) foot away.
The second "secret" to good production audio is a properly aimed microphone.
The mic should be above and in front of the speaker aimed at the notch at the base of the throat.
From there it is all about gaining skill and experience and improving your tool kit.
I can't understand the aversion to using interview mics when doing interviews.