Aizen was NOT nerfed

Sometimes I would see people saying that, due to the seals that were placed on Aizen during TYBW, he was heavily nerfed against SK Yhwach.

(All links lead to scans)

But he was not THAT nerfed, at least as nerfed as people say.

Aizen himself makes a comment in both the anime and manga that the seals don't actually nerf him in terms of reiatsu output and how strong he can be, but rather they just bring Aizen's reiatsu closer to him.

This isn't the only statement we get that is like this. We get another statement from Shunsui in both the anime and manga that says the same thing where it just keeps his reiatsu close to him. Even Mayuri admits that the seals were never meant to nerf Aizen in terms of reiatsu output and it was never made to make him weaker.