Tsunade was restricted, she choose to save everyone else, as opposed to fighting him head on.
Byakugou Tsunade wouldve been a match for him.
for one she is one of the Sannin, Two overwhelming power? She is a brute. Im pretty suresending chakra to her feet will help her resist the gravity jutsu, in addition to her brute strength/
With Katsuyu out, there will be no sneak attacks.
Tsunade fainted because of plot, her being active and letting Naruto fight wouldve been out of character and pointless.
Naruto became a village hero too early if you ask me.
Actually i heard that Kishi intented on her to battle Pein, it wouldve made the most sense.
Tsuande was beating herself up for letting Jiraya face him on her own. she wanted redemption of some sort.
It was foreshadowed that with intel, Jirayah woudlve won.
He even knew that she could possibly counter his technique...
But then
everything changed for Naruto to come and save the day.
Pein is like a Weaker version of Madara, so Hshirama wouldve beat him.
Tsunade is Hashirama without Mokuton, so I think the fight wouldve been fair.