[NOTE: Apologies for the mega-post. I've been shaping up to one of these ever since I finished TLD. For some reason the OP of this thread released it. Thanks, rbyrd!)]
I agree with many of the points you raise, rbyrd.
I was really surprised when I saw ROTE on the shelves in 2004 because I couldn't imagine how SRD could return to the story without making a mess of what he had already achieved. The series had reached a more than satisfactory conclusion for me.
Initially I thought that it was a cash-in by the author and his publishers and I didn't buy the book for a couple of years because I was afraid that reading it would tarnish my experience of the 1st and 2nd Chronicles. Eventually, I bought the book and began reading it. The start wasn't too bad, but as soon as it entered the Land I was shocked by how quickly it became unreadable. I trudged my way through it with gritted teeth. I also subsequently bought and started FR, but when I got to the part where Linden meets Covenant in Revelstone and the first thing that Covenant says is, 'Don't touch me!', I literally threw the book across the room.
It took finding the Watch and some serious advocacy by members on the part of the LCs before I finally went back and finished FR. It was still tough going but at least the part with Berek in it was well written and enjoyable. I can tell you that I passionately hated the Insequent by the end of FR and was not a bit put out by their demise (except maybe the Mahdoubt).
AATE was an almost intolerable grind from start to finish. Having TC back helped a bit, but it wasn't the characters that I found off-putting, it was the writing and editing. Hellfire, it was dire! I honestly don't remember if a single important thing actually happened in that book. And SWMNBN is the single worst thing in the whole series. Unbearable! (And, I believe, unnecessary.)
The treatment of the Giants, the Ramen, the Ranyhyn, the
Haruchai, the Sandgorgons, even the bloody Lurker reduced them all in my eyes. Just about the only creatures to emerge unscathed were the Wraiths of Andelain.
A good question to ask myself at this point would be why did I do it? Why did I persist with a reading experience that seemed only to yield frustration, disappointment and annoyance? A couple of reasons presented themselves initially: to find out what happened, to see if SRD could pull the mess out of the fire, to see it out.
After discovering the Watch a couple of more reasons appeared: to be able to be fully part of the Watch community, to be able to be involved in discussions like this and after finding out more about SRD himself (through videos, interviews and the Gradual Interview) to discover what drove him to write the Last Chronicles.
Because one thing I discovered is that he didn't do it for the money (it was something that he had conceived of many years ago). I also discovered that he is a person of immense personal integrity. This appeals to me. If I have a watchword (pun noted) it is 'integrity'. I have seen SRD say, on more than one occasion, that if you don't like what he is doing with the story don't buy the books. This is the ultimate critique. However, if you persist in reading on then, at the very least, you have to accept that the author has the right to do what he likes with 'his story'. At that point, while you can criticise how the author realises his story you can't really criticise him for writing the books at all or for the story he chooses to tell (not that that has stopped me

).
And now that I have finished TLD and the series I am finally beginning to get a sense of why he wrote it. I am finally getting to a place where 'joy is in the ears that hear'. My best guess at the moment is that the psychological/spiritual journey that TC goes through in the whole of the Chronicles mirrors a psychological process that SRD himself has undergone. Part of the reason that the LCs are so tortuous is that SRD himself found the final stage of the process tortuous. I now feel that I am fortunate (in spite of the grind) to have been a witness to that. In a way I feel that I have accompanied him on the journey.
Part of the struggle was letting go of some of the glory of the 1st and 2nd Chrons. In a recent interview (that I read or heard) he admitted (for the first time, AFAIK) that he got caught up in the huge success of the 1st and 2nd Chrons (they sold approx. 15 million copies). In the glow of that kind of success he was hurt and disappointed when his Gap books weren't as well received (
Mordant's Need did okay). I now see that one of the functions of the LCs is to take the gloss off what has gone before. It is a way of SRD bringing himself closer to the reality of his experience of writing the earlier Chrons rather than our experience of reading them. My experience of reading the 1st and 2nd Chrons was unalloyed (pun deliberate), SRD's experience of writing them and then living with their success wasn't.*
This is as far as I've got, but my experience with TLD and finishing the last Chrons has yielded far more than I expected and with at least a couple of serious fans yet to finish the book, no doubt, there are still more insights left to come.
u.
* I know that this is a bit meta, but with a writer of the quality of SRD there is always going to be more going on than just a straight-forward story.