It's not about the content of manuals (or at least it shouldn't be). If we took copies of all of the manuals of a successful airline and gave them to your shelf company, the outcome would not be the creation of another successful airline.
The substantive issue is (or at least it should be) whether an organisation has the critical mass of expertise, resources and competence to do the stuff, and then actually does the stuff, to produce the required outcome. And that's where the chronic problem comes in.
The chronic problem is that the assessment of those things is left to the subjective opinion of individuals in CASA, which opinions can and do differ on the same set of facts. And, more importantly, those individuals are unable to put a price on risk and decide when the entire costs of the mitigation of a risk outweighs the benefits. Any risk can be conjured into an aviation disaster, the mitigation of which is therefore simple in the case of 'little people': say no; stop it; ground it; send it broke; destroy it. That approach and outcome is zero cost for CASA.
If there were proper standards set, the pricing of risks and mitigations wouldn't be left to individuals in CASA. A proper standard is itself the decision as to the balance.