I looked into WW several years ago. While their mission is legitimate, I had several concerns. As some have already indicated, the organization spent lavishly on fundraising events and they had a higher than average overhead cost, owing to too many high salaried positions, mainly at their HQ in Jacksonville, FL.
The other issue to keep in mind is that WW only assists those veterans in need who were injured or otherwise need assistance after September 11, 2001. That leaves out Viet Nam vets as well as many others in need of assistance.
I do not know if they’ve cleaned up their act when it comes to overhead spending, but all legitimate charities are required to post their financials indicating overhead spending %, management salaries and so on. You should be able to find that information on line. Most good charities will have an overhead cost under 20%. I believe the United Way is in single digits, although they also suffered their own scandal a few years back.