I never liked the ending of this series, for one incredibly specific reason: it violated their own stated rules for how things work, and did so in a way that it completely failed to justify or explain.
Reality cannot exist without the Soul King. If the Soul King dies, the world just vanishes, he's the critical failure lynchpin for the entire Bleach multiverse. Furthermore, the Soul King literally has omnipotence, for all intents and purposes he is all-powerful and can do whatever the fuck he wants, nothing can defeat him, ever. Everything Sosuke Aizen did was because he was rebelling against the order of the universe: he saw the way the universe worked, did not like it, and decided to replace the current Soul King and change it, because he thought he could do a better job. This means, naturally, that the Soul King has the power to order the universe however they please, more or less. They must. And they do, we had that confirmed to us. By the same token, we had to stop Yhwach from absorbing the Soul King, at all costs, because once he did, he could succeed where Aizen had failed, he could do what Aizen could not: remake the universe in his own image, to shape it in a manner that pleased him.
These two facts, that the Soul King has this kind of power, and that without the Soul King everything just stops existing, are the core concepts of the ENTIRE series. Ukitake literally threw his life away to turn the arm living inside of him into a substitute Soul King, just to stop the universe from blinking out of existence because of what Yhwach was doing.
And yet, in spite of all that, Yhwach won. He fully absorbed the previous Soul King and became the new Soul King. That's it. We lost. Game over. Yhwach is now actually omnipotent: as if he wasn't omnipotent already with his own Almighty power, he now has that power but backed up with all the strength of the Soul King. There is literally not one single thing in the Bleach universe that could stop him, he can do whatever he wants.
Then Ichigo beats him anyway. He just beats Yhwach anyway, for absolutely no good reason whatsoever. Ichigo does it because he has to, not because it makes any sense. The only explanation we're given is some halfassed bullshit about Quincy powers that doesn't even make sense, because Yhwach was no more a Quincy at that point than Butterflyzen was a Soul Reaper. Two people who should not have been there appeared to shoot Yhwach with a projectile attack that should have never landed, to deliver a munition that should have had no effect both because Yhwach was beyond that and because Yhwach, as the progenitor of the Quincy, would have known about that trick and ergo been immune to it's effects, in the pursuit of a plan that makes no sense, trying to achieve an outcome that Yhwach's Almighty power both should have seen coming and could have retroactively edited to not happen even if he did somehow see it coming.
Yhwach can literally see the future, is immune to everything he knows about, knows everything about everything he has ever seen, and can edit the future even after his own death to come back to life if something somehow manages, impossibly, to blindside him in spite of all of this, because Almighty is a fucking temporacausal power, and it's absolute fucking horseshit. He literally has omni-precognition and can choose to ignore cause-and-effect, retroactively declaring things that happened as having not happened, or vice versa. He can come back to life by using the Almighty to clear that he just didn't die, it did not happen. In spite of all of that, Ichigo still somehow just fucking stabbed him, and it was all over.
That's fucking stupid. That makes NO sense, none, at all. The only possible way you could ever beat Yhwach is through time travel. I'm not kidding. Your only fucking hope would be to go BACK IN TIME, in the opposite direction that his powers (seem to) work, and gank him before he ever has a chance to start paracausally bullshitting you. And I actually assumed that's what WOULD happen, since Aizen was there, the Hogyoku could maybe get involved, maybe Ichigo would have to rewind and travel to the past to stop Yhwach before everything got to this point.
But he didn't. He just stabbed him. The end.
We were told that the Soul King is omnipotent and that reality cannot exist without the Soul King. The ending of Bleach, no, the last two CHAPTERS of Bleach, both just casually threw BOTH of those things out the window with a shrug and a wink. Ichigo did something to Soul King Yhwach that should not have worked, but it did. Then nobody questioned why reality didn't stop existing after Ichigo won. Then Yhwach tried to possess Ichigo's kid in the Epilogue, and got blown out like a candle, which... should have ended the world right there. But it didn't.
The ending of Bleach made no sense. None. It broke all the rules it had previously established, and didn't bother trying to explain itself at-fucking-all. As far as we can tell, everybody in the entire series was wrong about fucking everything, and a whole bunch of people died for no good reason. Which would have been a hell of an ending if that had been intentional, if that had been part of the plan, but it wasn't, because no alternative explanation was ever given for how things actually work, and nobody in-universe even noticed or commented on how they were wrong. I still love the aesthetics of this series and wish it could have gone on longer, I wish Ichigo's own powers could have been explored more. But the ending, not even the last arc (because I know some people don't like the Quincy, but I super do, I like the Quincy and I called Ichigo being one himself a long, long time ago), just the last five-ish chapters, just ruined the whole thing. It was a bad ending. I can't like it. Even if one of you swooped out of nowhere and explained everything perfectly, my problem would still remain, because wow, that's cool, thanks for making everything make sense! Now why the FUCK didn't that get explained in the manga, then?
My two biggest issues with this manga will always be that the ending was just total gibberish, and that Ichigo never got to explore or use his Quincy powers at all. If he was never going to use them, then he might as well have thrown them away when reforming Zangetsu, since having them ultimately did not matter in the slightest.
At least Tite seems to still be interested in the series, since he's done some official art for the Bleach gacha game, which shows off "official" appearances and depictions of some really interesting what-ifs, like Soul Reaper Tatsuki and Ichigo If He Only Used Quincy Powers.