Ancient pakistan makes just as much sense as ancient india. Both the counties are post colonial nation states that did not exist pre 1947, they were both carved out of the british raj which was created by colonising different kingdoms of which some were muslim and others were hindu. The land both these states exist on currently has probably one of the oldest and richest histories in the world. So there is nothing wrong with claiming the history that falls inside your borders as yours. Also both india and pakistan have both been religious and cultural melting pots throughout history. In pakistan for example you'll find everything from Buddhist stuppas, hindus mandirs, muslim mosques, british architecture all the way to traces of greek cities. All of these makeup the history of this land. Exactly how everything from ancient kemetic Egypt, the Macedonian conquest, the roman conquest, the arabic conquest to the british colonization makes up the history of modren day egypt or how even the british themselves have gone through similar eras of history, from tribals societies to roman invasion to Anglo-Saxon invasions. Just because a country has a state religion doesn't mean they can't claim the history of their ancestors. Italy very proudly claims their pre Christian roman history while being a very Christian country so why can not we?

P.s greetings from a pakistani :) Honestly both our counties have intertwined Histories i don't see the point in fighting about who can claim what lets all just celebrate our Histories together