Yes, I think that you've hit the nail on the head.
There is reality beyond the material, and there are spiritual beings there that want us to achieve spiritual freedom here and take dominion over our planet.
Many teachings have been released to help us come higher, sometimes those teachings have been corrupted by opposition, very true enough.
Anyway, the point is, no one yet, or very very few people yet, have actually followed the teachings all the way. As with any spiritual movement or organization, they have almost all lost their way.
It has almost always, in every case of any spiritual teaching, including Buddha and Jesus, and Yogananda, and all the organizations that have released teachings from the masters, become more about the outer organization rather than the inner truth.
A big part of this, imo, is opposition from the matrix itself. Truth here gets trampled quickly and most often even the messengers themselves almost always get caught in the trap of pride and ego.
That's why I've been stressing lately in my post, it's about being reborn, surrendering the ego completely, that is truly the only Way the infinite will be able to bring forth a pure New Earth through us.
That being said, the teachings are available on this planet for those that are ready to prove out the reality that there are no limitations other than the ones we collectively agree on. I like the book linked above (unveiled mysteries) and recommend it as a read
I also think the one you linked Sammy, "St. Germain on ALCHEMY-Formulas for Self-Transformation" is probably worth a read as well. I do think that organization did most definitely lose it's way, but a lot of the materials are interesting if you're willing to take them out of the box of the messenger or the organization itself.