But I think there's a large difference between "here's a first-pass attempt at a cost-effectiveness estimate purely so we can compare numbers" and "this is how much it costs to save a life".

You still have to answer questions like:

• "I can get employer matching for charity A, but not B, is the expected effectiveness of B at least twice as great as that for A, so that I should donate to B?"
• "I have an absolute advantage in field X, but I think that field Y is at least somewhat more important: which field should I enter?"
• "By lobbying this organization to increase funds to C, I will reduce support for D: is it worth it?"

Those choices imply judgments about expected value. Being evasive and vague doesn't eliminate the need to make such choices, and tacitly quantify the relative value of options.

Being vague can conceal one's ignorance and avoid sticking one's neck out far enough to be cut off, and it can help guard against being misquoted and PR damage, but you should still ultimately be more-or-less assigning cardinal scores in light of the many choices that tacitly rely on them.

It's still important to be clear on how noisy different inputs to one's judgments are, to give confidence intervals and track records to put one's analysis in context rather than just an expected value, but I would say the basic point stands, that we need to make cardinal comparisons and being vague doesn't help.