I think the word "illusion" is slippery, especially in the Eastern mystical context. We can say the ego's independence is illusory, for example, but that only means it's not ultimately real, which means we can be independent enough for our subjective purposes. Is the wealth of materialistic countries illusory? Perhaps their dominance will be relatively shortlived, but that doesn't mean the dominance has always been entirely unreal. The point is that illusoriness is compatible with some degree of reality, since illusions aren't nothing.