User blog comment:Eduardovongola/Renji Overpower/@comment-20612734-20131228150049/@comment-5398287-20131231013732

If they took everyone who had been beaten during the first (technically second) invasion, who would be left to defend Soul Society during the next, forthcoming, and likely final invasion?

Besides, as was displayed in the chapters prior, the captains who had their Bankai stolen found ways to become stronger by using their own unique abilities and not a general power-up.

As for Izuru, he's either 1. been forgotten entirely (which wouldn't surprise me given how much stuff occurred after he was attacked), or 2. he's just dead.