That's not what Itachi meant, he didn't say pretend to live in a dream and everything is real as long as you believe it, he was talking about lying to someone to manipulate them.
If that was what Itachi meant he would be supporting the IT not trying to stop it.
What's happening is very different, they are all trapped in cocoons and pretending that dreams are real, that's like locking yourself in your room and pretending your dreams are real, its childish and immature.
Also it denies progress, people live and grow from the problems in the world, if everyone was busy dreaming then no progress would be made, technology, new life from babies, and new ideas being born, everything will be trapped at a stand still.
Hopefully most of the SA are mature enough to realize that dreams aren't reality.