I don't agree with this. Remove the "Jon is a Targ" plot point from the story and Jon is happily in love with Dany even if his sisters don't like her much, Jon does not betray Dany, Jon has zero legitimate claim to the throne, Sansa does not plant the seed of discord with Tyrion. Tyrion does not share the secret with Varys. Varys might prefer Jon, but a lot of people knowing and liking Jon is not of much help. So when the bell tolls, Dany does not burn the city down, because she can actually rule as is. She does not need to be feared. People know and love Jon more than her, Sansa does not like her, Varys will keep a close eye on her, but she can rule, because her claim is not threatened by Jon's lineage, because there is no wedge between her and him (they trust and love each others without reservations), nor between her and Tyrion. She does not feel isolated, she can just take the time to get known and loved like she did several times before.
Now, if you think Dany would have burned the city no matter what, because she is mad, want to avenge Missandei and/or hate the people of King's Landing because they did not overthrow Cersei... I guess we can't agree.