novel - Is it necessary to take writing classes and learn formal fiction structure?

This is an offshoot from a comment exchange on an unrelated question. What to submit when asked for "sample chapters"?

I know a large percentage of traditionally published fiction authors, especially newer ones, have degrees related to writing or similar extensive education. And many people here talk about formal structural writing with terms I understand immediately (usually) but haven't ever heard before. I find it interesting and sometimes helpful.

But I was a bit surprised to have the above exchange where the other person assumed I knew this "basic" stuff. I don't mean the real basics like beginning-middle-end and so forth, but specific terminology and details like:

For the reader, an "inciting incident" does not have to be perceived by the MC as a big problem, it can start small. It roughly occurs about 1/8 through the story (by word count), and then grows for 1/8 of the story, to the point that when Act I ends (25% through the story) it is a crisis the MC must deal with. This later point (25%) is when the MC "leaves their normal world" (either physically or mentally) and begins to deal with their problem, usually reactively and unsuccessfully at first. (As opposed to proactively, starting around 50% of the story). (From @Amadeus)

I have no objections to using methods like this, I just never learned them. I took fiction writing and technical writing in college and, in grad school, I wrote tons and I also taught writing to undergraduates for 4 years, all essay writing of various types. I've been published here and there and haven't published something large because I never pushed myself to finish a huge project before. My critique group loves what I've got so far, but I guess I won't know until a professional editor gets ahold of it whether it's structurally sound.

I'm well into middle age and feel pretty confident about continuing to write without more formal training, though I've considered taking some classes (more for the deadlines than anything else). But I'm curious to hear other experiences.

QUESTION: In someone with a strong general educational background, what is the importance of formal fiction writing classes for writing a novel?