Conversation

Theory: although actual wealth inequality may not be vastly different, the philanthropy of Gilded Age billionaires (adjusted for inflation) was more beneficial to their local population than modern billionaire philanthropy.

Why? In the Gilded Age, you needed to donate your money near where you lived to secure your legacy (and because that was where your bank(s) physically were). This meant building Carnegie Hall or buying prime real estate to create a park, or establishing a perpetual scholarship fund, for example.
Now, there is no similar restriction on spreading your wealth throughout the world, so projects to improve the lives of people in far-off nations are feasible.

What this had lead to is the (arguably false) choice between solving, for example, hunger in Africa or solving homelessness here. While there is nothing that says a person with immense wealth could not split their money down the middle to both causes, it seems the ultra-wealthy prefer to focus the majority of their wealth on one problem with the intent to solve it, rather than half-fund a charity and rely on the donations of others to finish the job.

There is, of course nothing morally wrong with either choice: both building massive apartment blocks for first-world homeless and funding the eradication of malaria (primarily in Africa, but really wherever the plasmodia are found) are both objectively morally good actions.
However, it seems today's ultra-rich take a bit of a utilitarian view on what to do with their wealth and calculate that it is generally better to cure disease in poor countries than to house the homeless in rich countries.
It may be bias of history books, but the ultra-wealthy of the gilded age preferred to use their wealth to build a legacy by investing heavily in their hometowns. Perhaps it was that they had more ego back then and preferred to invest where others could see it.

How this has played out is that much modern local charity has to rely on "mere" millionaires and the everyman donation drive.
Millionaires seem to be just as ego-driven as the gilded age billionaires of old. However, their estates often only can only pay for construction costs. This leads to cultural institutions repeatedly engaging in unsustainable expansion projects because a local wealthy person wanted a wing named after them on the art museum, but was not wealthy enough to fund it in perpetuity. Other millionaires do not want to fund the first guy's ego project, so the project needs to rely on everyman donations or admission fees to be sustainable.
Everyman donation drives are highly unstable revenue sources because people tend to view all charitable causes as a fungible "charity" donation. Usually this is not a major concern, but years with a notably popular fundraiser show the weaknesses of relying on the public for support. Case in point: 2014, the year of the Ice Bucket Challenge. The ALS foundation got something like 10x its usual income that year, IIRC (which is a good thing, since ALS needs to be cured ASAP). However, many other charities found themselves way behind their goals near the end of the year and the TV was even more spammed with pictures of sad puppies and starving children. Why? People had already spent their entire charitable giving budget on fighting ALS and did not think to save anything for animal welfare or food relief. It doesn't matter your political stance, economic views, or belief in utilitarianism: charities competing with viral stunts is not a productive way to allocate resources and tends to create winner-take-all situations that give feast-and-famine funding to the agencies on the receiving end.

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P.S. Either of @USBhump or @USBloveDog asked me to post this, and I figured I should post here rather than as a normal @charizard for some reason. Feel free to discuss this with me or request that a specific one of us give our in-character opinion on your reactions.