Mary Greer has speculated that Waite may have had high-functioning autism, or Aspergers Syndrome. We don't know for sure of course but she was, I believe, making possible explanations for Waite's manner of expression some of the 'gaps' in the PKT current tarot students observe and other biographical information.
Also, Waite could not possibly have known that the RWS would become one of the staples of tarot. He wasn't writing for a world audience.
The PKT may not be all that some of us desire and I, personally, didn't like it when new to tarot. Nor did I care for the RWS, including Colman Smith' s art work.
When I understood more of the history, the personal experience of the deck creators and of symbolism and magic generally, I felt very differently. I see things in Waite that I did not see before. I am much further progressed in my esoteric understanding and practice than 12 years ago
I don't think I'd recommend the PKT to a person completely new to tarot but I would not use the phrase that the book is not all it could have been. Few companion books are all they could have been for any particular reader. Personally I now find some of the books I read at the beginning too wordy and too definitive and have given various ones away.
The PKT may not be all many people want now but it needs to be seen in the context of its time, and the capacity, individual preferences, knowledge and needs of each reader.
It is what it is and I do not mean to be obscure by saying that