Some properties you ascribe to the Tengrists, especially the quotation from Monge khan, were derided by Twentieth Century Western occultists as "fluffy bunny" occultism. That's a pejorative term for a haphazard mishmash of ancient religions. Well, it turns out the Twentieth-Century occultists were wrong. Tengrism was a "pure" ancient religion that had the many-paths feature that the occultists turned their noses up at.

Incidentally, we know almost nothing about Central Asian religion before the advent of Zoroaster about 3,000 years ago. Granted that Zoroaster was a Persian phenomenon rather than truly Central Asian, but it may be speculated that pre-Zoroaster Persian religion had features similar to those of Tengrism. Zoroaster was a huge proponent of Good-versus-Evil oppositionary dualism and the resulting intolerance of people one disagrees with; and it's very easy to picture that as a reaction against perceived excesses of a largely tolerant religion such as Tengrism.