I've found that once you have had the DMT experience, that you can read through spiritual texts outlining seemingly abstract concepts, and you will be able to understand what was being expressed on a personal level through first hand experience.
You will be reading the Baghavad gita, or bardo thodol, or the bible, or whatever, and you will stop and think "this sounds exactly like what I went through on DMT" it gives you a very deep connection to and understanding of deep spirituality.
For example, before DMT the Sufi concept of "fanaa" would have seemed fairly abstract, while after DMT I have a deep understanding of exactly what was being expressed.
Quote:Fanaa (Arabic: فناء fanāʾ ) is the Sufi term for "passing away" or "annihilation" (of the self).[1] Fana means "to die before one dies" and represents a breaking down of the individual ego and a recognition of the fundamental unity of God, creation, and the individual self.[1] Persons having entered this enlightened state obtain awareness of the intrinsic unity (tawhid) between Allah and all that exists, including the individual's mind. It is coupled conceptually with baqaa, subsistence, which is the state of pure consciousness of and abidance in God
-Wikipedia
Personally, if someone asked me to practice my spirituality without entheogens I would think it would be very difficult if not impossible, it would be like asking someone to cross the Atlantic ocean without a boat/ship, they are essential and crucial tools, however all they can do is take you to these places, the majority of the work still rests on your own shoulders.
-eg