Aizen just didn't cast it due to cockiness. It was also a plot device since Kubo made it too hax, he had to make it so that it wasn't cast on Ichigo. We know it wasn't due to overall power because it worked on Yamamoto and Juha Bach, both of whom were stronger than Ichigo or Yoruichi, Urahara and Isshin at the time. However ascended Ichigo and other ascended beings could possibly be too powerful for it to work since we do know that if there's a significant enough reiatsu difference, techniques can be bypassed. But even then it's a maybe. Dangai Ichigo while stronger was not so much stronger that Aizen wasn't able to put up a fight.