That's pretty much it, but I will take an opposing position that is, I admit, a difference only in the fine shading:
The Golden Ratio specifically as an aesthetic element is nonsense, but rectangles that aren't too fat and aren't too skinny are often a useful thing.
The Rule of Thirds specifically is nonsense, but sticking interesting things not in the middle, nor too close to the edge, is often a good idea.
Leading Lines, specifically, are nonsense, but sometimes an interesting thing's interest can be subtly clarified or enhanced with some lines (arrows, almost) that point to it.
and so on. In each of these idiot things there is a germ of an idea.
Are they pedagogically useful? Do they provide a useful stepping stone to the more important underlying principle, which is quite a bit more flexible than the "rule" or whatever you want to call it?
Undoubtedly they are useful for some people.
In many cases, though, and for many people, they actually obscure the genuinely useful ideas be replacing them with an easily memorized bit of dogma. I think they tend to freeze the mind into a specific shape, rather more than providing a stepping stone to something bigger and better. The underlying principles, the flexible set of ideas that something like the "Golden Mean" might represent, are simply not very hard. You don't need, in my opinion, to "ease into them with some simpler baby steps." You can just jump right in to the real thing, and ignore the simplified, inflexible, version.
I have, on several occasions, seen people reduced to shrieking maniacs over one or another of these things, insisting that Old Masters used these rules, and that I should just go look at some paintings. It became painfully clear that, while I had looked at a lot of paintings, the screamer hadn't. The screamer, in all cases, had been done some real damage by the rules, and was locked into an excessively inflexible state artistically, as well as a profoundly embarassing one intellectually.
