I agree, I've been suggesting this this for years. However, proportional representation is not easy.
One of the prerequisites IMO for PR is a more mature (stable) political system. Chances are that a hung parliament in Pakistan at every general election would be the most likely outcome. You then have to search among the largest parties who could form alliances to bring stable government. Significant political turmoil can and will be inherent in a PR system. That might be okay for a trustworthy sovereign in charge of an advanced republic like Germany, but in Pakistan it sounds like a risky prospect.
Another big risk is that you could cede political ground to extreme and fringe parties, this is the case with true PR systems, a small band of extremist members can threaten to bring down a coalition government and thus those few extremists often win unreasonable concessions. This also means that PR governments are usually much weaker, and way less stable. Also, all those people who are currently against Pakistan's political system as inept, corrupt, and useless, or those that are upset that PTI for example lacks the numbers and legislative power in the assembly to truly affect change... these people would find a PR system to be much, much worse. On this forum, I hear a lot of critics of democracy, and also people complaining that IK can't get anything done because of the limitations of a parliamentary system. A PR system for them would be way worse, IK would likely not have been made PM if PR had been in place. If a PR election were held tomorrow, the most likely outcome would be some messy and weak alliance of opposition parties. Conversely, the arguments in favour of PR are plain, and hard to ignore in a country that is as diverse as Pakistan.
So while I agree that PR is eventually the answer, I don't think we're ready for it. And it's important to note the shortcomings of PR and what it might cost us.