When I say Yamato hasn't really done that much I mean that none of her actions directly progressed the plot. Like, fucking Caribou did more to push the plot forward then she did
I agree that Yamato hasn't done anything to move the plot for but she has stopped it from completely ending
Like stated stated by other here
She stopped Sasaki from killing Momo and Shinobu, which would've destroyed the moral of the samurai and the raid would be over
She stopped Kaido from going down to the live floor which in the condition he was in he wouldve killed everyone before Luffy could awaken his Gear 5 and take him 1 on 1
She stopped the bombs from exploding and destroying the entire island which wouldve... destroyed the whole island lol
If you were to compare it to previous female recruits it kinda lines up
(even though I hate the parallel argument)
Nami, Johnny and Yosaku stopped the villagers from getting themselves killed in Arlong Park, which would defeat the purpose of them fighting in the first place
And Robin stalled herself from going through the Gates of Justice which again, the whole reason for them fighting