Atm, this signifies the huge problem with Bleach, namely that Kubo has been busy buffing Yhwach for half this arc - when he shouldn't even need it, while shamelessly nerfing the shinigamis, thus necessitating an galactic asspull at the end of the manga.
Reviewing Yhwach:
(a) He was around
or at Genryuusai's level BEFORE the invasion started(because otherwise he wouldn't have invaded in the first place)
(b) He then took charge of
Zanka No Tachi, possibly the most borked bankai in history, and definitely a huge power-up
(c) He then proceeds to start absorbing energy back from his own Quincies again, power-up #2 which in hindsight seems useless
(d) His
eyes(another OP ability) then awaken, letting him asspull out of the fight against Ichibei
(e) He then proceeds to absorb the Soul King
Just how many power-ups does he even need? I'm pretty sure that just stealing Zanka No Tachi should have been enough for him to win the war against the Shinigami, considering the return of Quincy energy each time one of them dies; frankly, I think he's one of the most mishandled characters in the entirety of Bleach, and considering how hyped-up people like Yamamoto were, it's a shame that while Yhwach gets all the buffs, they got rofl-stomped - Bleach would be a LOT more interesting imo if Bach had all the power-ups EXCEPT Zanka No Tachi, Genryuusai was alive, and we were shaping up to a final fight of Yamamoto + Ichigo + Shunsui VS Yhwach + Uryuu + Haschwalth, and I can but hope that Bach gets a heavy nerf(like the Soul King, existing inside him, eating away at his power) to make the fight more reasonable as opposed to obscene buffs VS obscene buffs.
Also hoping that Shinji and any other Vizaards left play a role here, since their hollow masks should act as poison vs the Quincies and could be one of the only ways to beat his OP guard(barring a return of the Royal guard).