These White Zetsu beings were manufactured in the tens of thousands before this war began with the help of the bijuu's chakra and there was never any reference to the offering of flesh and blood humans before now (unless you count their eerie desire to devour the corpses of humans). Without the Mazo, Zetsu, and/or Tobi having plunged into the depths of crypts and graveyards to ripen their armies without the reader knowing, the explanation has to be an alternative process like the bijuu providing life and substance to them as they were once brought into the world by Banbutsu Sozo. Maybe it's possible to create with just the essence of the Shinju alone - consequently, to make them without a human being playing the role of avatar they're just husks with untapped potential and minimal amounts of power (the human Zetsu might retain some traces of its old power if Spiral Zetsu is anything to go by).
Kishi seems to be treating this jumping from one villainous appearance to woe and despair, the crossing of swords, and then their sudden downfall as a process now. Kaguya just happens to be on the next rung of the hierarchy. She might be at the top though since the Jubi's authority is being upstaged by her having an even greater supply of chakra than it. Unlike her, the Jubi is a predictable, single-minded thing whose sole purpose is to eat all of the chakra that humanity stole from it. That kind of motive would be original amongst the various grey villains that have been thrown out mostly since Shippuden began, but Kaguya having more complex goals does make for more entertaining chapters than stopping a rampaging beast.
Unless a battered and broken Madara shows within the next few chapters, Hashirama's scheming to have Madara see the light through Sasuke might have been wasted. But how do you reform someone who has literally just had their body reconstructed to occupy the soul of another being? Madara's soul might not even be there anymore.
The anxiety and sweating shouldn't be a surprise with the grandeur of what Kaguya represents and how dangerous she is with the Shinju's power at her disposal. That can't be held against Sakura. Almost anyone who isn't a daredevil would be quaking in their boots too. Running-and-gunning was a luxury that anyone with auto-healing powers could afford. It allows you to make mistakes and approach a fight from a "tough it out" angle instead of acting on the side of caution. Madara alluded to that back when he first used Hashirama's powers. Sakura has relied less on trickery and other unusual tactics since she was taken under Tsunade's wing because her abilities respond well to a direct approach. But against someone who she knows is eons beyond anything she could muster, it would obviously be suicide to try and take Kaguya head-on.
Predictable or not, the best combat solution to this might be to give either give another boost to Naruto and Sasuke where they're able to match Kaguya or they channel their strengths together to attack. A third possibility would be to have Kaguya's parasitic turning of the world's population backfire on her and have everyone channel their chakras in an effort to destroy her. That would coincide with the idea that no one person should be stronger than everyone else. Everyone is capable of matching Naruto and Sasuke if they stand united.