Coulson talked about the Theta Protocol a lot. Well after messing around with the "real" SHIELD we found out that this was basically plan to bring in the Avengers. He had a video chat with Hill als sad "Yes. Let's bring in the Avengers."Expand on "use"
If I look at the MCU I have no idea what SHIELDS purpose is though, when Furys and Caps New Avengers (yes they are called that) basically replaced it.