WHO wasn't supposed to be a tool of soft power, and the fact it turned to one makes the decision to leave it all more valid. What soft power does a healthcare organisation provide, that couldnt be better served by your own means?
How do you feel about something like the International Atomic Energy Agency?
Showing up to do work is how you wield soft power nonetheless, even if it's a side effect.
I think you're confusing soft power with hard power.