It was not Shankara’s mission to recover and present the truth for universal application but to ‘establish the truth of Vedanta (i.e. of his personal selection of Vedantic maxims) by defeating in debate all who held an opposite view.’ (Pande: 1994) That admission all but nullifies his work. As Brahmin bookworm (i.e. scholiast) supporting Brahmin interests he collated a personally favourable (to Brahmins, but not to sudras) position and then selected and arranged suitable data from sruti (and which is ‘true because written’) to ‘prove’ his position. Shankara’s truth (i.e. ground of creation) finding method was rotten science. He simply copied his truth finding technique from previous Brahmin bookworms, such as, for instance, Badarayana or Nagarjuna (and who masqueraded as a Buddhist beggar (i.e. bikkhu) whose overriding aim seems to have been to degrade the archaic Buddhist dharma (= law, i.e. as set of rules derived from observation rather than books) by dissipating it in Vedantic lore/fantasy. The Brahmin Nagarjuna claimed that he took no position at all as he set about demolishing all Buddhist dharma positions/views).
In ‘proving’ that atman = brahman (to which he should have added = prajapati) Shankara blindly accepted the several alternate Brihadaranuyaka Upanishad propositions about the ground of creation. But that Upanishad had merely equated tautologies. For, the notions of prajapati, atman and brahman were but three different names produced by three different sources of speculation (in that Upanishad expressed in three chapters) about the origin and purpose of life. In other words, Shankara claimed atman = brahman (= parajapati) as creation ground rather than stating atman or brahman or prajapati as creation ground.
Had the youthful Shankara reverted to the insights of Veda (or the seasoned Manu) or simply to plain everyday (sub species aeternitatis) observation of (objective) nature his equation might have been a very uncomfortable because revolutionary but wholly liberating:
In other words, the atman/brahman/prajapati happens/acts as an ever presenting set of rules (or laws), indeed as a Turing Machine. Atman/brahman/prajapati is not an ‘imperishable’ substance/essence (already denied by the Buddha, but later upheld by Spinoza) but an ever ‘waiting/presenting’ set of (formation or selection) rules (or conditions), that is to say, the universal dharma (or any one of its localised elaborations).
Shankara, praised by all those who sought social stability, specifically the two ruthlessly self-serving castes on top of the pile, did immeasurable long term damage to India. He thoughtlessly accepted and so reinforced the atavistic and by his lifetime redundant notions of karman, samsara, dharma, the caste system, the varnas, the ashramas and so on within his seemingly sophisticated flaky metaphysics made irrefutable with 4 (sometimes 7) dodgy ‘proofs of truth’ (i.e. pramanas). Obviously, all the former become void if and when atman/brahman is conceived as unqualified, that is to say, as unqualified tattvamasi. By upholding the divisive (via arbitrary qualities) archaic social and so behavioural structure he locked India into a seriously primitive (i.e. infantile) past (i.e. as development phase) and so condemned India to philosophical and political stagnation and decay. A true avatar (as paramahansa) would have completed the transition from Veda (i.e. naïve, childish understanding) via the Upanishads (i.e. as adolescent/transitional understanding) to modernity (i.e. to mature understanding) in which all living creatures are and therefore are equal before the universal dharma/law.