Santa Monica, California, USA
Hi Turtle -- your argument kind of ignores Ogden Nash.
Chops: Re: "a poem could logically have more than one form of a metrical foot." I'm not quite sure how you mean this.
Francis Thompsons "The Hound of Heaven," for example, uses, all sorts of metrical feet, varying line lengths, and a highly erratic rhyme scheme. Yet, it is immediately recognizeable as a powerful piece of sophisticated poety, not the doodlings of an amatuer.
Pete and Deer would probably go batty over a piece like this. Thompson not only rattles the teeth of meter and rhyme from their sockets, he makes up some of his own words as he goes along.
So, of what use are rules? To master a form, a sonnet, for example, enables one to get a sense of meter, music, rhyme and structure. This is useful.
Merrill Moore, who died in 1957, wrote something like 60,000, no lie, sonnets. He figured out the rules, and they flowed from him as freely as water from a spigot. To which, some fifty years later, one can only say, "so what?" This was not useful. Moore was long on mechanics, the rules, but not a memorable poet. (To his more lasting credit, he was an acclaimed and innovative neurologist.)
What Moore, and most poets, could not do, was break the rules in a meaningful way after mastering them.
Shakespeare, who did not invent the Shakespearean Sonnet and was but one (the best) of contemporary practioners, broke "the rules" all the time, as he did in the "blank verse" of his plays:
"O, that this too too solid flesh would melt
Thaw and resolve itself into a dew!"
Ya flat can't force that into iambic pentameter, and yet they are among English literature's most memorable lines. Possibly be around a lot longer than anything by Poe.
I don't think that Pete's or Deer's appreciation of mechanics is irrelevant, but I can see a point to getting the basics down and then moving on from there.
I know, I'm rambling.