One way to measure an intelligence agency is how many times it’s in the news. The more an intelligence agency is in the news, the worse it’s. This is a basic rubric.
ISI has been instrumental in ensuring Pakistan gained nuclear weapons at a time the entire world was working to deny it access. It also ensured the defeat of the USSR. The manner ISI also trapped the Indian Naval intelligence officer working for RAW should be in textbooks. This three incidents alone suffice it to make the ISI as one of the top intelligence agencies in the world.
ISI is also remarkable in how none of its agents defect or is caught for the wrong reasons. One always hears Indian nationals being captured in India on a daily basis spying for the ISI. The opposite doesn’t happen in Pakistan.
The ISI also did a great job breaking the backs of the TTP and for making Pakistan safe in the last decade. In South Asia, it is the undisputed top intelligence agency.
But it also has some deficiencies. For example, it’s strength is derived from human intelligence. It’s not as proficient in technical aspects of intelligence gathering. This is a serious handicap in modern intelligence. Additionally, it has failed to foresee potential problems with the thousands of mercenaries that swarmed Pakistan during the PPP era. Contrary to popular opinion, ISI does a very bad job protecting the national interest. For example, media in Pakistan is very hostile to the national interest, what passes for critical inquiry in Pakistan is actually sedition. The so called deep state in Pakistan also is hands off politically which explains the revolving door nature of its politics where discredited politicians are recycled. Obviously, this could be due to the corrupt tendencies of the top military leadership which of course like any institution is a reflection of their overall society they come from.
Pakistanis should be proud of owning such a potent intelligence organization but it has some failures like all other intelligence agencies. It does a very good job to the job assigned to it. But this also shows its limitations. It’s not independent and is susceptible to exploitation by the military leadership which undermines its ability. Consequently, it is not able to carry out offensive operations on the lines of MOSSAD and others because the Pakistani state system in recent years has been very conservative and risk averse. This gives a room to its adversaries.