There is next to 0 growth opportunity. I was advised by multiple director level employees (15-30 years ahead of me career wise) to leave the organization. One said to come back at the end of my career after working for a place that was willing to invest in their employees. The other said to never come back and instead only be a consultant if I was still interested in NGO work. Over my 3ish years with the organization I constantly saw others in the early years of their career (2-5 years), highly educated and capable, leave the organization. They all ran into the same thing, lack of opportunity.
They are constantly outsourcing jobs to shared service centers around the globe, which is both able to cut the amount of jobs for westerners and they're then able to chalk those new jobs up as "program" related to boost their admin/program percentages. Obviously, this is great for those countries and their local economies, but terrible if you're looking to start a career here. The numbers I saw were something like 12 West African FTEs were the same cost as 1 American. Departments in the US are constantly trimming employees or not replacing staff when they move on.
On paper, all their "values" sound great. Unfortunately, once you're in the door and the higher you climb the more waste you see. Ex: regional meetings in Fiji instead of cost sensible hubs, etc. The vast majority of employees lack a sense of responsibility with regard to the fact that they're typically spending donations. I never have and never will give them a dime.