> As someone with some relevant industry experience, I can tell you that nearly 0 professional screenwriters or development executives are consciously sticking to a rigid structure as prescribed by some book.
I'd like to take your word for that, but numerous other insiders have said the opposite, and also noted a significant convergence around Snyder's precise timing breakdown since the book was published.
> The three act structure is, at the most basic level, just the series of beginning, middle, and end. Of course any movie has these sections by necessity
Traditional three act structure is more specific than that, it specified in broad terms what happens in each part, and, no, it's not fundamentally essential; there are other story forms, though they are rarely used in well-funded American feature films.