I mean I'm not too plugged in either but I feel like I see it about as often as I see complaints like this post. Also they do exactly that or sign and auction items for charity. I would say with their time and proportional to what normal people normally give the celebrities who are involved in philanthropy tend to give more than your average person and yet get scolded for it.

Billy Eilish recently donated 11.5M or about 22% of all of her money. Generally speaking we don't normally see people donating 20%+ of all of their money and I'm speaking about people who have the capacity to give 20%+. Now I'm sure there will still be people angry at what she chose to donate to or arguing that she didn't give enough and so on. I personally don't like people attacking philanthropy short of the charity being a scam. All giving is good and all publicity is good. For worthwhile causes and charities. I would much rather us focus our attention. On scam charities of which unfortunately there are many in this world.