Without quantifying anything it's kind of meaningless. The point is that recruiting is a business process and that we should treat like any other type of process, by being systematic.
The information we need is how many interested people responded with a generic message vs. how many responded to the personalized message, and the amount of time spent on each approach. Note that 'responded' here is defined as 'I'd like to pursue this opportunity' or 'I'd like to learn more' which then leads to them pursing the opportunity. Not social niceties like 'I'm not looking but it's wonderful that you took the time to read my Medium posts, you're so different from the other recruiters', etc.
The information we need is how many interested people responded with a generic message vs. how many responded to the personalized message, and the amount of time spent on each approach. Note that 'responded' here is defined as 'I'd like to pursue this opportunity' or 'I'd like to learn more' which then leads to them pursing the opportunity. Not social niceties like 'I'm not looking but it's wonderful that you took the time to read my Medium posts, you're so different from the other recruiters', etc.