We look different. There might be some overlap but personally I do not look like Modi
That is reason enough to draw a f**king line between the sand.
Imagine no Pakistan, and its Modi, not the prime minister but President of "Greater India". No doubt had India taken Pakistan they would have chanakyed their way into grabbing some Afghan territory. They would have erased and Indianized all Indus valley history and heritage, gone like the Buddha relics, defaced. That is a wet dream for Iranians too, they always have seen Pakistan as a hinderance to bordering India. What an insult.
Afghanistan is the final piece, if they become stable allies Iran is checkmate as China will check India. It's game over for India and it will balkanize which is long overdue.
Biggest issue unfortunately for Pakistan it has an ideological problem, the two nation theory simply does not hold in a changing complex world where hostile countries who have a more lets say rounded and a more "complete" ideology are able to influence easily in Pakistan. Its so obvious to see, a very religious person can easily be swayed to anyone, Afghanistan, Iran, Syria, Yemen, TLP, Lal Masjid, TTP etc. This is why Iran focused on Shiaism as it allowed them to have more ownership so ideologically they wouldn't be attacked by the Saudis. Same with Indians. So by binding yourself solely on two nation you are creating a weakness which is being exploited every time! Even the concept of Pakistan "not being Muslim enough" (which is ludicrous, I have never seen such devout people) therefore an enemy by Al Qaeda, what do you think will happen? There will be some who will diverge.
I guarantee you right now, mark my words, Afghanistan will implement sharia and at some point someone is going to come along funded and sponsored by abroad who will say "you are not following sharia properly" or "people are being baad" and the regime would be challenged. Its like going full communist and doing a Cuba
Is Pakistan prepared for that eventuality?
Even going attaturk would be a shift but it needs work to the point when the checkmate opportunity does present itself, there is ZERO RISK internally.