I think you're right, and the hostility you mention (wrt suspecting GoFundMe-s) is something (1) youth centric, and (2) weaponized effectively by people running scams.

I want to emphasize "youth centric"-- I think everyone I know (who is mostly 25+) feels the same wariness to Go Fund Me's and whatnot. I think we've all seen our share of scams.

And there's nothing wrong with the basic principle of "effective altruism"! It's the Effective Altruism movement of LessWrong types who'll throw out the vast troves of unquantifiable facts in favor of what they personally have the tools to measure and model. It makes them ignorant to their own insular culture, to the point where they are actually worried about, like, Roko's Basilisk.

But wanting to maximize the good that comes from your time/money/energy is still a good idea. I've donated exclusively to the two you mention (UNRWA and PCRF) for their long track record of making good use of their money, and not to any GoFundMe.

That said, I believe GoFundMe allows you to start a campaign in benefit of another beneficiary, e.g. this GoFundMe with the PCRF as a beneficiary. Who can say if the loss from GoFundMe's 3% cut balances out with a campaign potentially getting more people to donate