I only donate to one foundation now and I do not receive such unsolicited requests.

For context: a friend works at Cancer Research Malaysia and I've also seen some articles of her describing their success. She asked for donations in a post on FB and provided official channel directly to CRM, which then I contacted them directly and started monthly donations. I remember contacting their support for some bank-in Q&A, and I was happy to hear from a real person who didn't use any template answer.

Since then, I get a reminder monthly saying I'm about to donate X amount, but nothing annoying otherwise.