Stupidity: Ahsoka is fighting against the spear-wielding woman. She keeps blocking the spear using both her sabers. It would be very straightforward to block the spear with just one lightsaber (as she proves she can do just as well after she loses the smaller one) and use the second one to, for example, cut off the woman's hands.
Suggested correction: This is opinion, not stupidity.
Stupidity: Ahsoka gives the magistrate a day to surrender for no real reason - she has no advantage doing so nor it is any more honorable or humane; she is in fact giving Morgan time to organize herself with hostages as she explicitly threatens to. Had she finished her assault without this senseless ultimatum, barely anyone would have been in any danger or tortured for a full day like it happened.
Suggested correction: Tano doesn't know the strength of the Magistrate's forces. Djarin tells her that there are ex-military, hired mercenaries inside armed to the teeth and that he doesn't believe that even with the force she would survive. Tano agrees with this assessment and also asks if Djarin saw any hostages inside, so until then she didn't even know for sure whether or not there were. It is implied that had Tano continued her assault she would have been killed. There is indeed no stated reason why Tano gives a single day as an ultimatum, but it seems reasonable to assume that prior to meeting Djarin and The Child she would have used this time to plan her 2nd assault.
I think we disagree on the idea that it is implied that if she continued her assault she would have been killed; she killed 25% of their troops in their first assault, and then in the second one, which was in the open and broad daylight, she killed or disarmed everyone else including the main villain and the henchman, who was then killed by Mando, together with 2 guards. Mando was only instrumental in saving the hostages Morgan took after her threat - which, by the way, was expressed in a way that did not even imply necessarily that she was just taking the people hostages and not kill them right away as punishment. The evil henchman says it correctly "We'll be ready when she returns"; waiting only weakens her position in every way, since the stakes and/or disparity in forces is not shown adequately.
You seem to be ignoring the part where Djarin tells her that even with her skills she would be killed and she agrees. Whether or not that is actually true based on what we see doesn't really matter, it's their opinion based on what they know at the time. It seems fairly clear that she withdraws because she doesn't know what she's up against behind those walls.
She literally laughs behind his back when he says that line, and it is contradicted in every way from what we see, so it seems to be ignored by the writers first and foremost. They say the rule of writing is "Show, don't tell", I'd be fine with "Don't show the opposite of what you are telling." You can argue that it's more alike a plot hole than a simple stupidity, but I think you can agree that for what it is shown, Ahsoka had no other reason to wait for (more than) a day other than give the main character a chance to show up, and an ultimatum considerably worsens her position. It's not even clear why she took so long to make a move on the city, Bo-Katan (who does not have a direct path of communication on her) knew where she was, but the first time we see her it is also the first time she has a contact with the Magistrate.
No, I do not believe the writers included a laugh as an indication that Ahsoka believes the exact opposite of what Djarin states and that she agrees with his assessment that she is outmatched just to keep him happy. Yes, they do portray her as very powerful inside the city, but there are two people in there fighting at the same time which splits the enemies forces. Yes, giving yourself time to prepare also gives your enemy time to prepare. Sometimes there's no way to avoid that. This is neither a Stupidity nor a plot hole.
"Splits" is an overstatement; she takes the whole force down herself. We both agree that "she regroups after a preliminary assault and then prevails through teamwork" is the general idea of what it should happen, but it's not what it is shown. Remove Mando from the episode and you would only have (assuming she adopts the same effortlessy successful strategy to attack head-on a prepared enemy: she gets inside with no problem whatsoever!) a couple prisoners as casualties, which is something that Ahsoka herself brought upon her. There's not even an indication that she was preparing any strategy, since she asks about the presence of any prisoner while she is already going back to face the Magistrate.
