My head canon on the Bleach ending is as follows (after reading it like 7 times lol).
Way back around chapter 540ish, Yhwach goes on to talk to Uryu about how he's special and draws attention to the fact that he wasn't targeted by the Auswahlen. It's said in such a way that it wasn't Yhwach not targeting Uryu, but just that Uryu just didn't show up on his impure Quincy radar that he used to target all of them with the Auswahlen. This seems to me to be Kubo implying that Uryu is a blindspot for Yhwach's Almighty.
Then Haschwalth mentions that Yhwach putting all the spotlight on Uryu had the hidden purpose of making it so Uryu couldn't act on his own with everyone keeping their eyes on him. The only reason I can see for Yhwach doing this is that he can't "see" Uryu's actions himself. I think this is further supported by Yhwach seemingly being unaware of Uryu scattering those pieces of explosive paper, while Jugram did pick up on them. Uryu was planning to blow the Quincy palace to smithereens, yet Yhwach did nothing to act on the scenario, but Jugram say it immediately as soon as he got the Almighty. Haschwalth also comments that Uryu's ability is most suited for countering Yhwach's (it's called the Antithesis, very "clever" Kubo lol).
Ryuken inadvertently backs up this theory when he tells his son that he has to be the one to fire the arrow. Ryuken implies that Uryu is the only person capable of landing the shot, which to me further supports Uryu being a blindspot to Yhwach's Almighty. After all, Yhwach seemed surprised to be struck by the arrow.
As far as the arrow being foreshadowed, we are shown flashbacks of Ryuken gathering the Stil Silver from his wife's body and we are told the Auswahlen steals Quincy powers via clotting their heart with this silver. So I think of the Stil Silver arrow as being a portable mini-Auswahlen. It being established as a Quincy power robbing attack, in combination with Uryu being implied unseen by Yhwach as far as 100+ chapters before the end, in hindsight (which I know is 20/20) makes it seem like a very predictable outcome had you put together the pieces regarding Uryu and Stil Silver before the final fight.
Also, Jugram shows Yhwach the future vision of OG Shikai (which we find out is just his Inner Zangetsu) cutting him down. Yhwach thinks it's just a dream, but here's why I think he comes to that conclusion. There was no way for Ichigo to beat Yhwach on his own, he could only kill Yhwach thanks to Uryu's intervention, but as I said above I believe Kubo was trying to tell us that Yhwach couldn't see Uryu. So Yhwach was showed a vision where in his mind he just saw Ichigo cutting him and killing him. Which in Yhwach's mind can't make any sense because Ichigo has no special hax power, he's all brute and brawn, so seeing that his "dream" was so inexplicable he passed it off as just that a dream. And because he did that, he inadvertently set in stone that Ichigo would survive the encounter long enough to capitalize on Yhwach's kryptonite, Uryu, coming through to set up the kill.
I think this thematically fits Uryu's character as well, as he is the spiritual and literal successor to his grandfather's ideals, of working with Shinigami. In tandem with how Ichigo is the Shinigami who changes the Shinigami's stagnant view on the cycle of life. Together they represent a united front of Shinigami and Quincy that never happened so long ago, and that ended up leading to the fatal war in the final arc. For Uryu to be a rejected "unseen" ideal of a Quincy to be quite literally invisible to the father and representative of all Quincy is just the kind of symbolism I think Kubo puts in his work.
Of course this is just what I make of what Kubo has given us, but it's the most satisfying interpretation of the ending of Bleach for me personally that works on a narrative and technical standpoint.
Edit: I don't know how this got like this, but this was supposed to be a response to
@AnonymousBlank earlier post on Stil Silver lol.
I'm stating anything as fact.
