you also need barracks for troops, art that celebrates martial prowess, tales about the same. Yet we don’t find this among the Harappans
Nope, nope and how do you know?
The barracks are not needed and a number of civilizations had a warrior culture with out them. Art is not necessary and since you can not read the language how do you know there are no tales of martial prowess? What script you have could be a list of body parts chopped off or a recipe on how to make soup with the hearts of your enemies.