The Roads of the Foolish and the Wise 51
tasya kartāram api mām viddhy akartāram avyayam
“According to the three modes of material nature and the work ascribed to them, the four divisions of human society were created by Me. And, although I am the creator of this system, you should know that I am yet the non-doer, being unchangeable.” (Bg. 4.13)
It is not that this system refers to the perverted caste system in India. Śrī Kṛṣṇa specifically states:  guṇa-karma-vibhāgaśaḥ : men are classified according to the  guṇa  or the mode under which they are operating, and this applies to men all over the universe. When Kṛṣṇa speaks, we must understand that whatever He says is not limited but is universally true. He claims to be the father of all living entities—even the animals, the aquatics, the trees, plants, worms, birds and bees are all claimed to be His sons. Śrī Kṛṣṇa asserts that the entire universe is illusioned by the interactions of the three qualities of material nature, and we are under the spell of that illusion; therefore we cannot understand what God is.
What is the nature of this illusion, and how can it be overcome? That is also explained in  Bhagavad-gītā :
daivī hy eṣā guṇamayī mama māyā duratyayā mām eva ye prapadyante māyām etām taranti te
“This divine energy of Mine, consisting of the three modes of material nature, is difficult to overcome.