Charities have overhead expenses. This is not a bad thing. If your favorite charity missed out on a million-dollar donation because they spent no money on research, wouldn't you think it was false economy?

The charity has determined that the best marginal use of money for them at the moment is to improve marketing to get even more money. If this will ultimately lead to more being done for the CAUSE than otherwise, I don't see how one has reason to object.

You can, of course, criticize the charity for doing marketing studies if you believe they're wrong about their necessity.