Buddhism

That is a good observation and represents the Western insights into self and mind.

I agree, if you read the sayings of Christ, (and have some access to mystical or Gnostic teachings) then there is a very deep and esoteric teaching there and the semiotics are more obvious. During the time of the "Dark Ages" most information along those lines had to remain secret and esoteric on threat of death and groups developed and evolved within the context of the Mysteries, but they did have Christian underpinnings, but they were based more on insight, contemplation and knowledge and ancient sources of Wisdom that were preserved and passed along in that context. Of course, there were other reasons for secrecy, but this is not the place for that.

The Gnostics take on God and Christ was quite radical in itself and is rather interesting.

There is also the self-inquiry of the Hindu practices and what I consider the apotheosis of that in Advaita Vedanta, (def: not two, end of the Vedas). The approach starts with the logical premise that, I cannot be anything I can know. From there, one proceeds through one's knowledge, (body, life force, thoughts/emotions, discernment, bliss level = the five sheaths) in a process of elimination, (neti, neti). That leaves one at the Reality of Being itself, which one is but cannot know.

Teachers like Nisargadatta, Ramana Maharshi, Rupert Spira, are good resources along those lines and I have studied and practiced them. They are commendable and to the point or, hard core, as I like say. I eventually found some issues regarding extremes and other factors by way of comparison and in relation to the teachings of buddhadharma, which, in a sense, was like an upgrade overall.