The biggest constraint is often individual people’s time/attention; additional money is only slightly (if at all) helpful for the already rich.
But a little bit of money goes a long way to help people who are not eating well, don’t have a place to live, need to work 3 stressful part-time jobs to make ends meet, ...
Massive inheritances (dropping someone tens of millions of dollars or more) are one of the greatest problems in our society. The top marginal tax rate for inheritances should be 90%+, and we should be cracking down hard on all the sneaky ways people hide gajillions of dollars for their descendants. Maybe with an exception for small family farms, since presenting farmer sob stories is one of the biggest ways billionaires have figured out to market their intergenerational hoarding.