I see others have noticed the It's A Wonderful Life similarities too

So:

His few dollars contribution to Ndugu was the same as George Bailey *(i) saving his brother's life, (ii) rescuing the entire town from the greed of Potter, (iii) avoiding Donna Reed becoming a spinster librarian, (iv) saving an entire ship full of American servicemen, (v) keeping his town from turning into a den of sin, (vi) making it possible for scores of middle-class families to own their own homes in a pleasant neighborhood, instead of renting cheap tenements, (vii) keeping the distraught pharmacist from being sent to prison, (viii) saving the kids the pharmacist inadvertently killed and (ix) getting Clarence his wings? I think I missed a few there, but that's the gist.

Really. I don't see that parallel at all.

The whole point of IAWL is that a lifetime lived with character and virtue benefits the world in ways that may not be obvious, but that are more important than a single act of heroism ... and that, by being a good person, you win the true affection of your fellow people, which is more valuable than material success ("My brother George: the richest man in town!").

It isn't that if you write a few checks to charity, you're a good person.

Schmidt undertakes a sort of review of his own life, though not one quite as direct and literal as Bailey's. What he discovers is that, not long after he dies, it'll be as if he had never lived.

The letter sent on behalf of Ndugu is a bit of a grace-note, so to speak, in an otherwise sad story. But it's an ironic one. What gives it its punch is that he realizes that his connection (modest as it is) with Ndugu is more rewarding
than his entire life's work.

At the beginning of IAWL, George Bailey thinks his life has been a pointless waste, but by the end he (and we) realize it has, in fact, been "a wonderful life." At the beginning of this movie, Schmidt thinks his life has been pretty good (though perhapse short of "wonderful"), but by the end he (and we) realize, it has been more like a pointless waste.
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* It's possible, I suppose, that there is someone in the world who's never seen "It's a Wonderful Life."