Firstly, I am un Urdu Speaker myself who once used to support MQM in its fledgling time pre mid 1980s but I early on saw its Fascist nature and moved away from MQM--and I was right about that switch as I feel I am right about moving away from Imran (not necessarily, from PTI) about 15 months ago.
On topic: Urdu as national language is not an issue--it never really was. What choices the West Pakistanis had in 1947? Arabic? Turkish? English? Urdu has organically become the lingua franca of Pakistan and that's excellent. There is no point debating that by referring to languages in China or Japan etc.
About Karachi, the issues are of governance and on that score, I believe Jamaat e Islami would have been the best (minus some of their social policies) but now the Mayor of Karachi, who is himself an Urdu Speaker and is a capable administrator, has no excuse because he also represents the party in power in Sindh. I'm willing to give him a chance!
Also, while Urdu Speakers should fight for their 'rights' for a fair share of the govt. jobs, it is in the private sector where they should focus on for improvements. And Urdu Speakers are generally better educated and 'urbane' gives them advantages and indeed they are among the more prosperous communities of Pakistan. What have the Sindhis achieved by getting govt jobs??
PS. Pakistanis are generally ingrates!! The State of Pakistan maybe this or that but still provides them a lot very cheaply! My tuition at the Univ. of Karachi in the 1980s was about $15/Semester. That college education enabled me to come to America and comfortably get TWO Masters from a high ranking Public university. Many faculty members had PhD from UK universities and some even went to America on Fulbright Scholarship. $15/semester!! A friend from the NED University in Karachi also got a degree and got his own Masters in America and is now a very successful Mechanical Engineer in America. That friend's brother has three late-teen/early 20s kids who are getting scholarships and great education in Karachi and yet the brother always complains about Pakistan!! My brother in law in Karachi recently had tinnitus and turned out a benign tumor and he got free/almost-free some kind of laser treatment a few months ago to take care of that. While here in America, despite a good medical/dental insurance, I have paid $4000 in dental bill so far this year!! I am sure the list can be long if we all include our inputs. But I hope you get my point!!
There are positives and negatives. But PDFs constant breast-beating is just a too negative.