I don't understand what you're saying. Suppose I was (hypothetically, counterfactually) in danger of legal persecution as an apostate. That danger would be in the way of my having fun. Then I would want being an apostate to be legalized. Whether I achieved that by donating to a charity or any other way is instrumental.

It's incorrect that in general, donating to a charity is never useful to me personally. I have type 1 diabetes; I donated to the relevant Israeli charity, which lobbied the government, which included insulin pumps in the social security net (medications that every tax-payer has very cheap access to). I gained actual money compared to paying out of pocket for the pump (although I didn't do that), and I gained fun (using a pump is much more fun than manual injections).

Or: someone donates to SI; this increases the chance of successful FAI takeoff; they go on to have fun forever instead of dying of old age.