How do we evaluate whether a one-on-one is productive? How can a business, in aggregate, learn from the hundreds of independent weekly manager-employee meetings

How do we evaluate whether a one-on-one is productive? How can a business, in aggregate, learn from the hundreds of independent weekly manager-employee meetings to see what kinds of issues keep cropping up? This of course presumes both a good manager and an employee who is willing to speak candidly with them. This may not always be the case. (How often is it not the case? Let's examine the data and see! Maybe there is a systemic problem with trust between managers and their employees that needs work?) It is not uncommon for businesses to periodically do "employee satisfaction surveys." I don't think crunching data to measure the effectiveness of management (which affects employee attrition) is ridiculous at all.