Why would any leader in their right mind gennins in what I consider to be a super A rank mission. Failure of the mission would mean that Orochimaru (konoha's greatest threat) would get the Sharingan).
Any normal leader would see in a second that this mission is too important to place in the hands of gennin, no matter how short handed on jounins they are.
What was Tsuande doing anyway? I'm sure she could have left the administration of the village to the elders, and gone after Sasuke herself.
Shikamaru's team is incredibly fortunate to be alive, let alone be able to drag an unwilling and powerful traitor home.
I think Kishimoto allowed this lapse in judgement to happen just so we could see the gennin team in action, and to advance the plot.