AdS/CFT fell out of string theory. It's only holographic in the sense that in some circumstances you can summarise an n=dimensional system using n-1 dimensions - not in the literal sense of using the kind of optical transforms that make visual holography possible, but in the more abstract sense that all of the information in some spaces ends up on a notional surrounding boundary.

The AdS universe is basically a mathematical toy for physicists to play with. It doesn't correspond with the physical structure of the real universe. There's a hope that it might correspond to some kind of mathematical meta-structure that defines physical laws.

This article suggests that's very unlikely.

Personally I wouldn't be surprised if AdS/CFT turned out to be a dead end - probably like supersymmetry - and the real structure of quantum gravity turned out to be completely different and unexpected, and not a Conformal Field Theory at all.

But IANAP, so I may well be wrong about that.