I mean, herein lies the philosophical argument of opportunity cost to society in general. Every thing we spend money that is, perhaps, any amount over-engineered or nice-for-nice sake, or made of slightly higher grade materials, or, well, anything other than strictly utilitarian and minimalist as possible is technically consuming opportunity cost that could benefit society.
If I order wings with my pizza tonight, as I have done, and I decide to consume both of those things, instead of donating the money on the wings to someone else, I've directed excess to myself instead of to the betterment of society. And obviously that's the reductive, logical conclusion of the argument. What I'm getting at is that it's an interesting mental and philosophical exercise to figure out where that line lies. Does it lie with $400M super-yachts? Sure, probably we don't need that wealth going directly to propping up the yacht industry, which, itself, doesn't need to exist from a utilitarian perspective. But I'm not sure how to define where that line lies. Is it the old "know it when you see it" line? If I buy a 26' sailboat, is that still falling into the ostentatious conspicuous-consumption-that-could've-been-spent-on-others? Of course it is. What about a jet ski? What about a $400 kayak?
I'm not sure the answer here. I agree with your core sentiment that "I wish people would flex their donations to effective charities" in that it sounds lovely. I struggle with the idea that charities have to exist to patchwork fix parts of society and government that are inherently broken. Creating a construct that inherently hyper benefits a small coterie of people and necessarily introduces some inequities, and then hoping that that same small coterie of people will feel just guilty enough to donate to others to try to whitewash some of those problems... is inherently flawed. Obviously.
But I also recognize that the downstream and upstream of the middle of the bell curve of capitalism is basically what powers almost all of our jobs. We work because we produce something that someone, somewhere wants. Or needs, sometimes. But a LOT of it is "wants." And if it was _just_ needs, the economy would be an even bleaker place. We've seen what that looks like too.
That being said, I personally feel like, you know, a clever tax policy helps with a lot of this, if it's underpinned with effective enforcement and effective oversight and efficient use of those funds. But boy are those tricky.