I am the proud owner of all 5 five volumes and Digital Typography. I have been in front of a computer for almost every single day for around 45 years. I speak and write several languages, including Chinese and Japanese. I am regularly coding in several programming languages and consider myself fairly fluent in things like HTML and CSS. I have worked as a typesetter and assistant editor of two medical periodicals.

I could go on but what else in the world do I have to add to that so I can say "as for me, I opened the TeX book, read it, and understood it" or "I know how to use LaTeX, confidently"?

I don't know the answer to that question, but I do know the answer to the question "is TeX / LaTeX a well-designed, user-friendly, sane software?". The answer is no, no, and no.

Millions of people love to use LaTeX and use it daily. Your experience is just a personal opinion.

Millions of people love traffic jams which is why they're happy they can have them twice a day.

Your claim is just a claim.

Oh definitely, let’s do a PhD in Latex and its worthless toolchain before start writing the actual thesis.

Software should be invisible and not a hindrance to our ability to express ourselves.

Reading a single book is not equivalent to a PhD in LaTeX.

A single book on latex only covers you until the introduction of your thesis. Then you will need to add a table. That’s a different book. Then you will need to align your equations. That is another book. Then you will need a graph. This is a freaking library of books.

I mourn for the time I wasted on Latex. For nothing.

That's not even close to be true.

Oh, you mean those 500 pages of dense Knuth writing?

Dense? The TeX book is a total delight to read.

Not for people who are fun at parties