In all honesty, I suspect that most people believe Shizuko is a sorceress already. I mean, lands she tends to flourish beyond all reason, her enemies sicken and die, terrible plagues are tamed by her works,
and there are those wolves that follow her around everywhere... She says she does it all through the technologies and methodologies she promotes, but who could possibly achieve such results with a few trinkets? She even cultivated shitake mushrooms, for goodness sake.
And that's just for the people in a position to actually hear about the details. Most people aren't going to hear much past "Lands under her supervision are more than ten times as fertile as anywhere else".
All these old men going "Oh no how dreadful that this girl that has stayed so loyal to us and so helpful to us and has been doing nothing to help our side to flourish and advance at unprecedented speeds, she's too dangerous, too smart, too resourceful, we must get rid of her NOW and get rid of all these advantages she's been providing us!" are getting really annoying.
Sadly the 'stop being so exceptional, you're making the rest of us look bad' mindset is very much a real thing, and thats before you bring pride and gender biases into it.
Many of those characters have ambitious.
The series isn't showing, but Oda Nobunaga was a "bad boss" that didn't inspired loyalty.
But now with Shizuko's helping him it becomes more difficult to for him to fall.
Or worse, Nobunaga could use her to punish them for their "failures".
In addition to these reasons, it should also be noted that the structure of government was somewhat more...
Fluid, during the Sengoku Jidai than what we'd normally think of. It was extremely common during the time period for retainers to overthrow an incompetent daimyo, and more fighting actually took place within a territory than between rival daimyos; Nobunaga himself spent a lot of years putting down rebellions, before he had enough ducks in a row to start seriously contesting the alliances formed to contain him.
This was, in large part, because of how retainers were gifted land as being
theirs, instead of just being administered on behalf of their lord. It was how things was done at the time, but... Well, it meant that they had little stake in improving
Nobunaga's position. They don't get any richer when Nobunaga does (trade excepted), and Nobunaga conquering new territory just means more rivals in court. Taken to extremes, it could be argued that they
benefit if Nobunaga is doing poorly; if he has to focus on internal affairs, there's less chance of being asked to contribute to wars of aggression, and they have more leverage to make demands of him.
So Shizuko doing all sorts of great things... Well, at best she's not doing more for
them, and at worst, she's a threat to their autonomy. Once the large-scale infrastructure projects she asked for get underway, that could change some minds, but at the moment, she's
Nobunaga's miracle worker, not theirs.
And specifically in the context of a difficult military campaign like this one... Well, war is their entire reason for being in this time period. Military accomplishments are what earn you rewards, and justifies your privileges. So if she's doing that so effortlessly that you're left just standing around... Well, how are you supposed to demonstrate your talent to your boss? Heck, what challenges and sacrifices can you even point to in order to prove your loyalty? It's hard to ask for new positions when you don't have anything to make your case with...
Or to connect that more strongly to this chapter; in history, military accomplishments took Hideyoshi from being a common footsoldier to declaring himself kampaku. If Shizuko does all the heavy lifting instead, though... Well, it's hard to see how he'd ever rise to similar prominence.