Not exactly. Corruption isn't the problem with the army for the most part. There are a lot of other problems. The most important being inertia. The army is still focused too heavily on infantry, which is cheap to acquire, but very expensive to maintain. This causes problems like their real-estate dependency, which then introduces avenues for corruption.
Corruption is always the biggest problem in all countries and organisations. Why can't the Army get reformed? You say inertia, I say corruption.
Why does COAS along with his accomplices (Corps Commanders) couped the civilian government (hint: its corruption and consequently treason).
Why is the military interfering in all aspects of governing Pakistan(economy, diplomacy, social)? Corruption again.
Inertia can legitimately be a reason for an organisation to be slow in changing, but "inertia" (what you describe Pakistani Military to have) is basically just another form of corruption at this point.
Who is delaying changes, why?
Is it so they don't lose their jobs? (Mild) Corruption.
They fear they will lose power? (Serious/sacked) Corruption.
Fear of their salaries and kickbacks getting reduced/eliminated? (Jail) Corruption.
Sometimes we say corruption as a word but we don't fully understand what corruption trully is. Either for fear of losing money, power or job, it is always corruption. What differs is the form and the seriousness of corruption. For example, stalling changes for fear of losing your job due to structural changes that would improve the organisation is definetely corruption (from the organisation's perspective), but it is a "logical" corruption for a human to have. Can ultimately be a sackable offence (in serious countries) but usually its a reprimand/official-warning. In any case, you can understand why people feel and act that way.
Now if the corruption is due to fear of losing power then this is definetely a much more serious offence. If the fear of losing the job can maybe cause a reprimand, then this form of corruption is definetely a sackable offence and probably entered into a black list for ever again getting into any high/managerial position in the government.
Corruption is ethereal and never-ending. We may invent new words for it, but it is always there waiting and plotting. Just to clarify, legit inertia exists, but from what i am seeing so far in Pakistan's military, it has "inertia" (corruption)