The trouble with consciousness is that it is abstract. The conjecture of “nothing really exists except consciousness” requires “consciousness” to be concrete so that it might be transmitted. Consciousness therefore requires something to detect the other objects of which it becomes conscious and something in which to store and organise the sum of the consciousness. More than that, it postulates that, to have any purpose, some use must be made of what now becomes known, otherwise everything becomes merely an observer of everything else and there is no action and without action, there is nothing of which to be conscious.
The other problem is that the conjecture requires each and every subatomic particle to possess consciousness, because that is what sentient beings are made of. Stones, etc would be conscious as would all the elements.
The problem is that we know that the elements and their constituent parts behave predictably. e.g. hydrogen atoms would have new experiences, of which they are aware, each day; a 100 Million years old rock would be, in our terms, immensely wise, far wiser than us. A star, trillions of times bigger than us, would be unbelievably wise, regardless of its age. In fact, wisdom would be a solely a product of age and size. The bigger you were the more consciousness you would have.
I suspect that this is a theory only held by people who are unusually tall and morbidly obese.