Even then, he didn't even know that what he was writing was
part of his mythology. After all it's by his admission that Elrond was only in the Hobbit because he ran out of names and other references to the Silmarillion [for example the swords] were to "give the illusion of depth". And I'm evaluating the novel as a narrative on it's own, not a vignette from a universe. I'm not debating structure as a the creative element of "creating a world" but the structure of writing a plot.
But to go on more specifics
ntertwining those two stories would have produced a confusing jumpiness in the narrative forcing the reader to repeatedly and rapidly switch gears between two totally separate storylines
There are a plethora of novels and literature that have succeeded in intertwining plots and avoiding confusion, many of them sharing an "amazing web of interconnectivity". Considering this is the epitome of this in your estimation, there would have been little difficulty linking the "totally seperate storylines". The pressures of a different medium and commercial realities forced the film interpretation to present the stories intertwined [I'm sure even the most zealous of fans would have been disconcerted if they hadn't] and with no difficulty. There shouldn't be because the practice of telling parallel plots has been used for hundreds of years, and anyone who has been exposed to fiction in that time should have little difficulty following it.
As far as an accurate estimation of intent can go, to look at his own writings and the drafts relating to that part of the novel [as published by his son in volume 7 or so of the Histories of Middle Earth] it seems quite clear that he would pursue one narrative sheerly because he had no idea where to take the other.
But there is no need to claim genius of purpose here, because the point I'm making is the success, evident as it is, is made in spite of the lack of orthodox narrative structure. No defence of the works is necessary, because the evaluation is not necessarily judgemental.
When you do know what has already happened.
I must stress that we are talking about two different things here. I am evaluating LOTR as a narrative, and not as a window into the greater mythology of Arda. When I say he had no idea of what would happen, I speak about the plot of LOTR, and important events as being important events in LOTR. I am judging a narrative and not a vignette. If we were to judge the purpose of the author, he set out to write a narrative, not to extend on his mythology. Which explains why and early plot involved Bilbo visiting Britain.
The following quote might illustrate the amount of knowledge that he actually had towards the plot that was being laid out as he wrote it. (it's scanned, so parts are a tad 1337)
1 met a lot of things on the way that astonished me. Tom Bombadil 1 knew already; but 1 had never been to Bree. Strider sitting in the corner at the inn was a shock, and I had no more idea who he was than had Frodo. The Mines of Moria had been a mere name; and of Lothl6rien no word had reached my mortal cars till 1 came there. Far away 1 knew there were the Horse- lords on the confines of an ancient Kingdom of Men, but Fangorn Forest was an unforeseen adventure. 1 had never heard of the House of Eorl nor of the Stewards of Gondor. Most disquieting of all, Saruman had never been revealed to me, and 1 was as mystified as Frodo at Gandaif's failure to appear on September z2. J. R. R. Tolkien, in a letter to W. H. Auden, 7 June i955
Which brings us back to The Old Forest as well, because that was one thing that was intended from the start, and was derived from earlier work [i.e the Poem "The Adventures of Tom Bombadil"], but that had no relevance to the mythology. The events there still hold no bearing on the greater plot. I vaguely understand you claim about revealing a facet of the ring, but what facet is revealed has no integral place in the plot and even then the immense amount of space given to the sequence, especially when compared to later sections can hardly be justified under How To Write.
And even then I feel the sequence with Bombadil and the ring is about the nature of the former, not the latter.
You'll also have to excuse the fact I haven't read any of this since before High School, so I'm working from memory.
But more importantly, we're evaluating seperate things. I'm not judging the work harshly in the light of it's lack of structure, I merely see it as a curiosity, and as Yak says, it carries it's own charm as a result of the extraordinarily unorthodox way with which it is written.