Nagato's deva abilities and Itachi's yata mirrors could prove them useless.
Defense with Shinra Tensei for Nagato creates a five second cooldown between attacks that would leave him open during that time. Itachi's use of Susanoo's defenses wouldn't be useful for prolonged battles since using the ability takes enough of a toll on Itachi's chakra and health, and prolonged is the likely scenario for this match considering the two Naruto ninjas would have to pull their strongest attacks just to try surviving here. A casual Cero from Ulquiorra is capable of destroying multiple city blocks, while the mentioned bigger feats of durability and destructive potential for the Naruto ninjas are their trump cards.
Itachi and Nagato have many techniques that could one shot Ulquiorra.
Doubtful they have "many" as you claim. Itachi's only decent one-shot kill ability to pull here would be using Susanoo's Totsuka Sword, which would be ineffective here thanks to Ulquiorra being in flight. Amaterasu and Tsukuyomi would also be ineffective thanks to Ulquiorra's flight and speed advantages. As for Nagato, any variant of Shinra Tensei would be ineffective for offense here thanks to the mentioned advantages for Ulquiorra. Chibaku Tensei would also prove ineffective as Ulquiorra is more than capable of powering his way out of the attack and the attack taking a heavy toll on Nagato's chakra reserves.