You are thinking about it the wrong way. You don't spend $45B on stuff for yourself. You spend $45B on changing the way governments and populations live work and how power is balanced.
When Bud Fox asked Gordon Gekko "How much is enough" Gekko knew immediately that Fox wasn't in the same league. Money isn't about stuff, it's about power and influence.
I think new rich crowd will almost completely replace old generation wealthy in next 50 years or so. People who are born in this decade will have very hard time understanding philosophies and life style choices of Gorden Gekko.
See: The Millionaire next door
World is a strange place. Very few millionaires win and lose spectacularly. Nearly all of rich people out there are silent and invisible.
Peter Thiel, the godfather of "today's centi-millionaires", has a butler.
— At least he had one in 2007:
just because via social media you see more of the "new rich", which have desire to make public statements and be as visible as possible, doesn't mean that's all there is.
It's nice when vanity projects end up helping the masses (and we'll have to wait and see how successful it is at that). However, we shouldn't act like this very public display of wealth (again, before anything is even done) has motives that are so different from, say, giant statues of oneself or giant mausoleums.
"Everyone ... wants to shape the world in their specific ideal."
Most people give up on this idea in their mid-20s though or never really believe that they can.
Yes, well that's 100% the distinction.
The OP seems to think that the obvious choice is for money to "go to something meaningful" without specifying what "meaningful" actually is. Within this context, that would seem to mean the "meaningful" thing is "greater -good" charity. My point is that more frequently, this type of money go toward direct influence of power like setting up Super PACs, hosting power networks like Sun Valley Conference, establishing think tanks, grants to universities for certain research etc...
$45B is even overkill for that. Each presidential candidate spent (or had spent on their behalf) roughly $1B in 2012. Zuckerberg therefore could have doubled a candidates spending for each presidential election for the rest of his life and still have half his fortune. $45B is that huge.
EDIT: The multiple downvotes seem to indicate I said something that is disagreeable. I'm not implying that buying elections would be a better use of Zuckerberg's money, just that he has so much money that elections are just more "stuff" he could buy without even thinking hard about it.
And you will.