I agree with your sentiment. Sometimes we get articles on (say) the Fourier transform, with its own intuitive take on how and why it works, some visualisation and some maths. I think these articles are great. I can understand how they would spark the interest of someone who is not familiar with the maths, whatever their age.
That's not the case here. I don't think that anyone who has upvoted this has read any significant part of the document, simply because it would take months if not years to go through. It's like me posting a several-hundred page set of homemade notes on cell biology and saying "Notes to take you to medical school level biology".
Fair. I happen to agree that the document is probably not going to be of much use to anyone who hasn't already studied the material.
I do, however, firmly believe that anyone - no matter their age - may find interest and cause to learn math, even if starting with high school calculus.
That's not the case here. I don't think that anyone who has upvoted this has read any significant part of the document, simply because it would take months if not years to go through. It's like me posting a several-hundred page set of homemade notes on cell biology and saying "Notes to take you to medical school level biology".