First Pak institutions need to investigate all candidates before election, at least from big parties. Most PTI MNA's will be disqualified under article 62 but we all know it will not be implemented. Which beg the question, is article 62 only used to remove elected PM to create instability?
If institutions can't do their work before election then why create chaos for next 5 years? Now they are warning Shehbaz Sharif for court case, why they don't prove it now so ECP can disqualify him before election is held next month? Why they will wait till he become PM? I don't think country can work like this if half the time PM is fighting cases in court when elected, otherwise he is fine.
That means the ECP isn't working like it should. However, they couldn't have DQ Nawaz in 2013 because they did not have the necessary information back then. Shehbaz Sharif has nothing that shows he is dishonest and won't be DQ under 62/63. He can be disqualified for being convicted of a serious offence, but that will have to be done by the NAB.
I agree when you say a PM can't work when he's taken to Court every few months but this was his own doing. He refused to be investigated any other way. The SC has mentioned all the reasons why they even entertained the petition in the first place. Had he let the Parliament investigate it wouldn't have reached the SC.
In essence, NAB should have dealt with it, but everyone knows NAB won't. The Supreme Court stepping in was a good option when there was visible miscarriage of justice by NAB and the rest of the accountability set up of the country.