Try https://www.charitynavigator.org , which tells you what percentage of donated money is directly spent on the cause versus administration, staffing, etc. Charities vary widely, and it’s worth comparing charities in the same space, e.g., healthcare, hunger relief, veterans, because different spaces have different overheads.
Not so much the problem.
The bigger issue is a ton of foundations are just bribery enabling organizations. There's a reason pretty much every politician and rich person has one.
Donate $10k and the foundation can pay for a lavish speaking engagement in the Bahamas. The foundation head can give a 10 minute $50000 talk about how poverty is bad and then they enjoy the open bar and conversations with rich and powerful people.
Let's be frank, the average citizen isn't giving a dime to the George Clooney foundation for justice [1]. So you have to ask, why does such a foundation exist?
[1] https://cfj.org/
I don't know anything about the CFJ, but their 990 from 2024 suggests that they really aren't spending much on overhead besides wages and salaries[1].
[1]: https://projects.propublica.org/nonprofits/organizations/813...
And Susan G Komen has a 93% rating on that site. What an absolute joke.