Buddha was a Gnani, but his interpreters are not. Buddha did not enter into scriptural interpretation. So the Vedic people threw him out of their religion.
Advaita sages agreed in nearly all points with Buddha. Buddhism has failed through misunderstanding Gautama and believing that nothing is left to exist after Nirvana. What is it that sees the illusory nature of the finite ego? This is what the Buddhism need to answer and cannot on their theories.
Advaitic sages say:~ It is the Seer. The Buddhists are in error in regarding the finite ego as illusory, and as having nothing more behind it: but they would have been perfectly correct in such outlook had they added the notion of the Seer or Witness. How is it that Skandas come together and compose the ego? Who sees them come and go? It is the Witness or the seer, the Atman, which is in the form of consciousness and through by amazing the formless witness and witnessed (universe) one becomes aware of the existence of the formless witness mentally.
When they say that, the mind comes and goes they are forgetting that there must be another part of the mind as consciousness which notices it and which tells them of this disappearance and appearance. All their misunderstandings arise from the fact that Buddhism does not penetrate to find the answer to the ultimate questions. The truth of a single reality within or underlying the illusory universe or mind is all-important and without it Buddhism becomes fallacious.
The ultimate truth can be realized without Buddhism or Advaitic teaching if one is ready to inquire analyze and reason on the base of the true Self. Therefore, it is necessary to make sure of the fact that, the 'Self' is not the form but self is formless, then rectify the reasoning base, from form to formless to understand, and assimilate and realize the Advaitic truth.
Mundaka Upanishad:~ This Atman cannot be attained through study of the Vedas, nor through intelligence, nor through much learning. He who chooses Atman—by him alone is Atman attained. It is Atman that reveals to the seeker Its true nature. (3 –page-70 Mundaka Upanishad Upanishads by Nikilanada)
When the Upanishads says: the human goal is to acquire Self-Knowledge and they indicate the personal gods, scriptures, worship and rituals are not the means to Self –Knowledge, then why anyone should indulge in it. The religion, concept of individualized god and scriptures are the greatest obstacle to Self-realization because they are based on false self. The seeker of truth has to search the ultimate truth without losing himself in the labyrinths of philosophy, through deeper, inquiry, analysis and reasoning and assimilate and realize it.