It is clearly evident (and King said himself) he did not know where the story was going or how it ended. That is reflected in the unevenness of the tale, and the unsatisfying endings for many of the major characters such as Randall Flagg, Eddie Dean, Mordred, and the Crimson King.
I am aware to many who find this series beloved that it’s about the journey and not about the ending, but there is a fundamental flaw in that thinking in that, if the ending was not thought out while writing more than half of the books, then how could the journey be rewarding when in hindsight much of it feels aimless.
This may be harsh but it is my frank opinion after spending nearly a year reading this series.
Epics such as these need to be plotted and thought out, so that the themes and character arcs can interweave and lead to a resolution that feels fitting, and leaves the reader with a burning sense of satisfaction. Imagine if Harry Potter or Lord of the Rings were written as sporadic as the Dark Tower? You could imagine there would be many detours and side quest that would feel pointless to the overall plot of the book.
To clarify, I do like the literal ending of the series, as in the final chapter and the Coda, i agree with King that that ending is the right one. When I write about King not knowing how the series would end I meant from an overarching climax and resolution that starts in Book 5.
Did I also enjoy many parts of the series? Of course I did, and it’s a testament to Kings ability as a wordslinger. But this work by no means elevated him as a writer and does not enhance his legacy. He is at his best writing single novels where he takes a single situation, idea, or theme, and hammers out a character story. IT, Misery, The Shining, Pet Sematary, The Green Mile; those are all stellar novels that execute on this premise.
Kings mechanism for writing does not apply to multi book series. He doesn’t or can’t write like that, and it’s what’s necessary in those types of stories.
As a final word, the series gets worse as it goes. Books 1-4 are actually the strongest, as they hold all of the promise and set up that does not get delivered on in the final 3 books. They take a 19, Ka, metafictional, fate driven plot to the brink of annoyance that detracts from the characters agency and motivations.

Not the ending I expected, although I probably should have expected it.

Çok az kurgunun sonunda öylece kalakalırım. Çok eserde karakter ölünce hüzünlenirim. Adı üstünde kurgu, yazarın hayal dünyasının bizim ruhumuza dokunması.

Çeşitli mecralarda finale dair eleştiriler okumuş olsam da ben sonu çok beğendim. Üzerine uzun uzun da düşündüm. Bu yüzden hayatıma bir şeyler katan kitaplardan diyebilirim.

***BURADAN SONRASI SPOILER OLABILIR***

Ah be üstad, Jake'in ölümünü böyle acılı yazmak zorunda mıydın... Oy'un tutuğu yasa rağmen sahibinin sözünu dinleyip sonuna kadar Roland'ın yanında kalmasını neyi düşündün de kaleme aldın. O nasıl bir hayal gücü? Jake ve Oy benim en sevdiğim karakterler oldular bu yüzden kitap bitti ama ben hâlâ içime öküz oturmuş bir halde etrafa boş boş bakınıyorum.

Bu yüzden son sözüm

Ake!

*** SPOILER SONU***

What a journey this was! Right now I’m just sort of letting everything marinate. The ending…oh my, that ending. I should have seen it coming, but I didn’t.

Dark finale to King's epic series that ends the only way it could. Love!

BROOOOOOO!!!! thousands of pages later i am finally done with this godforsaken series. brilliant [ending] IMO. main criticism: i hate the way stephen king writes plot points so abruptly just to keep the story moving-it was really making me question whether i liked this series at all the whole time i was reading. (not to mention the weeeiiird angry black woman buried in susannah’s consciousness??) but here i am with the book closed in my lap, heart aching for characters i thought i didn’t care about. what a beautiful journey.

It's a doorstop that's for sure (and I listened to the audiobook, but it increased the weight of my iPod so much that I could have used it for a doorstop), but all in all a satisfying conclusion to the series. At points it did feel like it could have been broken into two or three more books, but maybe King was being nice and not making his fans spend the extra money it would have cost to get the additional volumes. I don't really want to say much more so as to not spoil it for anyone, but I will say I was worried after such an epic tale that the ending would fall flat, but I was definitely satisfied.