Simple as that. When you send proxies to fight wars on behalf of your army. You treated it as a game. It's win-win, just brainwashed kids with some guns. Pak Army can concentrate on internal matter. It is a game for you too. If you have so much love for Umma then why you are dead silent on Uyghur issue or the Rohingya issue. Or the Syria or Iraq issue.
Your real reason is the mere boogeyman scare, you are afraid of the water wars (which will soon happen if this kind of a relation is progressed) that India will essentially make you run dry of water. That's why we signed such a stupid water deal 80-20 share
. Nowhere in the world water is shared in that scale. Even the Kashmiris weren't happy with such a deal. Hoping this would end the Kashmir issue, but alas you started again.
Kashmir is of strategic advantage for you. It is very close to Delhi and it will be strategically huge disadvantage when north India gets strategically weak. So, we are never giving up Kashmir even if it comes to the Kashmiris we can't risk majority of population for a few minorities.
Pakistan's demand will not end with J&K. There is a lot of Muslim majority places which by your logic belong to Pakistan. This will go on and on.
Plus government India cannot give away any territories on their own. Even if government decide to do that Court can interfere and hold the deal because, the accession was a legal one unfortunately for you not between the British and Maharajah of Kashmir but with government of India and the later.
Lastly what legitimacy you have over Kashmir when you sold chunk of your P O K to China.
Oh we don't have some super love for Kashmir, they eat up our resources. Kashmir has special status which no state enjoys. and still there are issues.