Regardless, Nobody showed off any new abilities past what they had before they went there. Kenpachi just used something he learned a while back at the request of his superior. Renji should be nearly the same level as Ichigo, and with Uryu, they should be stronger than Ichigo. And they couldn't beat the number 8 guy? While Ichigo beat the number six guy by himself? The power levels are out of whack.
Of course Ichigo IS the main character... but Renji is the main character's friendly rival, who SHOULD be equal or around the same strength. (Of course, this makes Renji viable for a captain position, which I think he would be fine at. Why haven't they promoted him?)
Because Ichigo's reached a higher level over power than them by controlling his Vizard powers. He's only been able to win against any of the arrancar in Hueco Mundo by putting that mask on.
Uryu meanwhile was only able to beat a captain by using the Quincy Final Form and sacrificing his powers in the process. Having only just got them back, I'm guessing he doesn't want to lose them again. As for Renji, yes he's powerful, but there's a huge gap of power between captain & lieutenant. Kubo essentially said himself (through one of the characters) that the captains of the Gotei 13 are the backbone of Soul Society's fighting force. So yes, he's powerful, but it would seem that all the captains are still more powerful than he is. Plus, they all have way more experience, apart from possibly Kenpachi, but he became a captain through pretty unique circumstances.
And don't forget that when fighting the 8th Espada, Renji was unable to use his bankai. At first, anyway. By the time the limit on his & Uryu's powers were lifted, they were both really worn down while the Espada had barely moved and was able to heal himself by eating his subordinates. All of Ichigo's fights were straight-off 1-on-1 encounters with no limiters like that and I think he would've been beaten by Nnoitra if Nel & Kenpachi hadn't stepped in. Let's not forget how badly Ulquiorra owned Ichigo without even using his zanpakuto, and with Ichigo using both his bankai
and Hollow mask. He would've died right then if Grimmjow hadn't turned up with Orihime.
There are a lot of factors to consider with Bleach battles & power levels. Why does no-one ever pay attention to them?
