Who said anything about full force? I can see you've never trained at an MMA gym, where we make contact every day and still manage to not get injured at any sort of above average rate.
That's something I hear a lot from guys that don't train contact actually. There seems to be a belief in those circles that's pretty common that the human body is made of glass and will simply shatter of first contact. That's really not the case.
The worst part of getting hit is psychological, which can only be overcome by getting hit. People that aren't used to that 9/10 times simply panic when it happens, rendering all other training useless as technique flys out the window.
I agree it's important that to build fighting ability, you regularly get hit for all the reasons you say. The ability to not lose your head when you get punched right in the face is really important, and can't be taught without actually getting punched right in the face.
But I don't agree that every single drill you do, you need to get hit. There are certain drills we do where I'm trying to train something specific, and being hit in the face a lot would not enhance that particular drill. In those situations, I pull each shot before it lands. But on Monday night sparring nights we hit and get hit tons, and if I don't see a punch coming, I eat it.