I’m a trial by fire guy. Theories of fighting don’t interest me nearly as much as the actual doing of it. Heck, I frequently don’t even like watching it, unless it’s one of our guys. I tell people who want to come watch my tournaments they are welcome to come, but bring a book!
I mean, centerline, for example. I could talk endlessly about how slipping out to in reclaims the center line so you can apply forward pressure in the form of combinations, and slipping in to out takes you off HIS centerline while keeping him on YOURS so that angled attacks (hook, overhand right) have greater effect (harder to block, body out of position, they have to adjust before they can return fire etc). You could practically write a book on the subject!
I just find reading about it to be kind of boring. I’d rather go get hit in the face and not think about the concepts of the centerline and ask the more fundamental question of “how do I move here and not get hit,” until I’m not hit in the face anymore
Boxers do it simple “GET OUT OF THE WAY!!!” “DON’T STAND THERE AND LOOK AT WHAT YOU DID!!!” “MOVE!!!” That’s pretty much what Dave yells at me, rather than providing a 10 minute dissertation 
I’d rather develop sensitivity by grappling than read about yielding, etc.
Don’t get me wrong, I appreciate that the centerline is a useful concept but there’s no need to talk it to death, IMO. Of course, I"ve done just that now, so in conclusion, I’d just like to say
“Pot, this is kettle… YOU’RE BLACK!!” 
I also don’t think all books are useless. I’m sure I’ll accumulate some over my life 
I will also amend my statement to say that if you are already familiar with something, but can’t quite seem to get it, sometimes something in a book will make you go “AHA!!”