If I'm donating money to fight cancer, and the majority of the money goes to administrative staff, that's inherently a flawed charity. It's exactly what led to the downfall of the Susan G Komen foundation.
There's also a death spiral problem. If donations drop and administrative costs stay the same, that charity's ratings only get worse.
There's a reason most examples of successful non-profit unions all rely on steady streams of government grant funding.
What do you think the core purpose of the Wikipedia Foundation is? Do you think the engineers who write the code and operate the site are “administrative staff”?
Is there any charity (older than five years) where the majority of the money doesn’t go to administrative staff?