First, Save the Cat is a popular and widely read screenwriting book, but it's hardly the most popular and most widely read screenwriting book. Second, though Blake Snyder put his own spin on structure, he's basically offering a variation of the three-act structure laid out by Syd Field in Screenplay (originally published in 1979) - and Syd Field was working from ideas laid out by Aristotle. So no, Save the Cat is not the guidebook for every Hollywood movie.
There are other questionable assertions in the article. It implies that Blake Snyder is responsible for blockbusters being targeted toward teenage boys, when in fact that started in the late-70's after Jaws and Star Wars introduced the blockbuster era. Save the Cat was published in 2005. It also claims Snyder was the first to specify page numbers for structural beats when, again, Syd Field did just that in Screenplay. Finally, it repeatedly says Save the Cat's structural breakdown gives a "page-by-page" formula. In fact, Snyder identifies fifteen structural beats. Unless you're making fifteen-minute movies, it's obviously not a page-by-page formula.
The biggest logic hole in attributing Hollywood's originality problems to Save the Cat is the historic time line. Many older movies follow Snyder's structural beats perfectly. In fact, if you convert page numbers to percentages of pages, most of Shakespeare's work fits pretty well. Even the Slate essay uses The Matrix as an example despite the fact it came out six years before the book.
When I read the Slate article I debated whether it was worth mentioning in this blog. Who really cares if it's being trumpeted by wannabe writers and lazy critics to justify a feeling of superiority over people who actually make movies? And it probably helped sales of Save the Cat. After all, if you want to write Hollywood movies and someone told you there's a book that all professional screenwriters use as a guide, wouldn't you buy it? (For the record, I think the book is quite good, though the structural stuff is its weakest part.)
But there's a bigger subtext here that appears regularly among aspiring screenwriters (including, occasionally, students of mine): That structure is a restrictive formula that inhibits creativity. And the inverse of that is often promoted by screenwriting "gurus" - that good structure is the key to good movies. Both of these ideas are not only wrong, they're dangerous to new writers.
In fact, structure is an element of craft. Understanding it is no different than understanding exposition, character development, or even grammar and spelling. It's a tool to tell the story. The story you tell can be original or derivative, imaginative or trite - regardless of whether the underlying structure is solid or not.
The parallel in architecture would be knowing the engineering required to keep your building from collapsing. You can make a beautiful building or an ugly building, but first you need to make sure it's not going to fall down!
The fundamental concepts of three-act structure are found everywhere - in European films like Amelie and art films like Beasts of the Southern Wild and classic films like Casablanca. Even, as I mentioned, the work of Shakespeare. Would you call those "formulaic"?
In fact Shakespeare worked within very rigid ideas of what a play should be. He even had to write in iambic pentameter! And he obviously didn't do that accidentally. He was well-educated in his craft. (I wonder if the Shakespearean version of Slate proclaimed iambic pentameter as the reason for unimaginative playwriting.) But Shakespeare accepted the traditions and conventions of his craft and used them to tell stories that have stood the test of time.
The danger of ignoring structure is that if your story is not well structured, it will likely have dull parts and logic holes. Counter-intuitively, it will often be predictable. You might get lucky and instinctively give your story a solid structure. But if you resist learning this aspect of craft, you will not be able to fix a story when instinct fails you. And it will.
On the other side of the coin, the danger of believing structure is the sole requirement of a good screenplay is that you might fail to do all of the other things necessary: create dimensional and compelling characters, build dramatic scenes, and write sparkling dialogue. Not to mention have something of value to say! Solid structure is the beginning of the process, not the end.
And whatever source you go to in order to learn structure, I encourage you to apply your own critical thinking. I don't like assigning specific pages to structural beats, either. That doesn't mean there's nothing of value to learn from Save the Cat. Take what makes sense to you and ignore the rest.