The teachers of philosophy and leaders of mysticism or religion do not want to inquire into the truth and have no time for it.+

Isa Upanishad says: ~

Andharh tamah pravisanti ye Vidyam upasate,

tato bhuya iva te tamo ya u vidyayarh ratah.

Into blinding darkness enter those who cling to ignorance, but into still deeper darkness go those who flirt with knowledge. It is the promotion of nescience with the help of scholarship to justify the worship of a mortal in place of God. It makes no difference whether God is conceived as clothed with attributes (saguna) or as absolute attribute-less existence (nirguna).

Sage Sankara:~ VC Let erudite scholars quote all the scripture, let Gods be invoked through sacrifices, let elaborate rituals be performed, let personal Gods be propitiated---yet, without the realization of one‘s identity with the Self, there shall be no liberation for the individual, not even in the lifetimes of a hundred Brahmas put together (verses-6)

Sage Sankara said: ~ Neither by the practice of yoga nor philosophy, nor by good works nor by learning, does liberation come, but only through the realization that Atman and Brahman are one in no other way. (1) Vivekachoodamani v 56, pg 25

Lord Krishna confesses that the oldest wisdom of India (Advaitic wisdom) has been lost: people misinterpret and falsify it today as they did then. It is not yoga but the philosophic truth. But nobody knows it. 

The teachers of philosophy and leaders of mysticism or religion do not want to inquire into the truth and have no time for it. (Gita –Chap- IV-v.2)

In the Gita Chap.IV where Lord Krishna says: ~ "This yoga has been lost for ages" the word yoga refers to Gnana yoga, not other yogas: the force of the word this is to point this out.

Lord Krishna describes some of the other yogas, but devotes this chapter separately to Gnana Yoga. So one sees even in those ancient days, people did not care for Advaita; they wanted religion; hence, Gnana got lost. That is why Krishna calls it "the supreme secret." Krishna points out that the yoga must-see "Brahman in action."

Gita Chap.IV: "He who achieves perfection in Yoga finds the Self in time." This means that after his yoga is finished, he begins the inquiry into the ultimate truth, and in due course, this inquiry produces the realization of the universal spirit as the result.

Lord Krishna says Ch. V:~ “Those who know the Self in truth.". The last two words (tattvataha) are usually ignored by pundits, but they make all the difference between the ordinary concept of God and the truth about God.

There is no need for any practice to realize the ultimate truth or Brahman, or God. Perfect understanding and assimilation of ‘what is what’ is very much necessary to realize the ultimate truth or Brahman, which is God. : ~ Santthosh Kumaar