1) In response to my viewpoint, I am a student of the University of Exeter's Master's programme for Western Esotericism and an administrator on Esoteric Archives. I assure you there is no miscommunication concerning the flow of human history and the role of esoterica within that flow, and if there is a strong civilizational/ethnocentric view, it is of the influence and participation of esoterica in the history of the Western world from Pre-Socratic thought to the current day.

Please inform me of your definition of 'human'.

To the comment of the whole of Romantic to Modern publications consisting of solely 'facile misunderstanding' invalidates the very basis of the initial primary question that sparked this discussion. Why discuss this modern publication if it is naught but 'facile misunderstanding'? Please illustrate an example of enlightened understanding to allow a comparison.

2) The Picatrix, Hermes Trismegistus' Asclepius, the Orphic Hymns, the writings of Jabbar ibn Hayyan, etc. were all available before the Gutenberg was a factor, and in fact contributed to the Renaissance of the 12th century. Only education provided a barrier of access to these works, and certainly nothing directly attributed to an inner circle or cabal of esotericists.

Furthermore, the assertion that esoteric content was meant to be misunderstood is fallacious. The purpose was for it to be rather clearly communicated to those who had carefully educated themselves (such is the case with Alchemical art and the traditions of allegories reaching back to Zosimos of Panoplis). It was devastatingly unsafe to have literature connected to the secrets of immortality and the creation of gold, and, again, the secrecy ensured safety. I reaffirm that mere education provides the barrier, not some conspiratorial cabal purposed with disinformation to create and ensure a 'pseudo-public' discourse. Even your example of the Masnavi is merely limited by education (though I'm curious what you'd define as 'really' understanding).

Is there a filter in esotericism? Absolutely.

Is that filter intentionally created to ensure the idea presented is communicated to a specific group? Yes.

Can this same filter be ascribed to any language, science, art form, culture, etc. in existence? Yes.

Ascribing your filter to occult symbology only functions if you choose to define different forms of language, mathematical expressions, and infra-red radiation as occult symbols.