So do we live in a hologram? Even if the AdS-CFT link proved fruitful for tackling quantum gravity, if we were able to find a way to navigate the challenges and make this technique relevant for the universe we live in, it doesn’t mean that we actually live in a hologram. It’s a mistake to make the jump from “AdS-CFT provides a handy way to solve gravitational problems” to “our universe with gravity in three dimensions is an illusion, and we really live in a two-dimensional boundary with no gravity.”
A mathematical contrivance, as handy as it may be, doesn’t necessarily dictate our views of the fundamental nature of reality. If holographic principles are useful for solving problems, it doesn’t necessarily mean that we live in a hologram. And even if we did live in a hologram, we wouldn’t necessarily be able to tell the difference anyway.