For another, as a sibling comment points out, AOC can have a much greater impact by influencing policies that help the people than through charitable donations, which, let’s face it, are just a bandaid on the structural issues that lead to such wealth inequality. Making something one’s professional goal when in a position of influence is much more impactful than optional activities on the side like charitable donations.
But the reason it's a "fallacy" is AOC could donate 100% of her current salary for 63,000 years and that would equal 1% of Elon's current net worth.
Even if you did get 1% of Elon's money, it wouldn't be enough. Real change comes from structural change, not pure cash.
And as the original person pointed out, you're clearly smart enough to know that.