Kabbalah is a science, and Kabbalists are scientists who realistically reveal the concealed, Upper World and the Unified Force, the Creator. The revelation happens by correcting one’s nature and transforming it to the nature of the Upper World.
There have been Kabbalists who revealed the concealment (Tzimtzum Alef and Tzimtzum Bet) of the Worlds of Atzilut, Beria, Yetzira, Assiya and even the World of Adam Kadmon and the World of Infinity, along with the governance by one and three lines, and so on. Each Kabbalist made a revelation to the degree of his correction.
But as long as the souls are fine (not very egoistic), Kabbalists are unable to reveal very much, since they lack a big enough instrument. The Reflected Light (Ohr Hozer) is weak and does not reach the higher levels. Therefore, the Kabbalists of the past revealed creation in general, without the particular details.
As time went by, the same souls went through many reincarnations and accumulated additional egoism (Aviut) and desires. Thus, they became able to work with a more corrupted material, which is why they conducted a deeper research of the matter of creation, the Creator’s work (Avodat HaShem).
This research is similar to research in any other science. However, the external science provides an external knowledge and attainment, meaning only about our world. It doesn’t change us. Kabbalah, on the other hand, gives us a higher mind and sensations, correcting man himself. This is why we find our way into a new world. It’s because we change and the world changes as well.