My guess: It focuses on land, which is not a thing most Americans think about a lot, especially these days.
And this is a shame, because really, Georgism is about so much more than land.
"Land" should be read as a stand-in for all the things that humans merely seize and divide up among themselves.
Every machine, every building, every vehicle requires some input of human labor and ingenuity to create.
But it also requires natural resources, which humans seize and divide up instead of working to create.
But this division matters, because human effort and ingenuity are things we want to reward, while nature's bounty is something we want to divide equitably.
It should be about a general approach to constructing an economy: "Reward human input, divide nature's bounty equitably."
This policy was Georgist in the general sense because it rewarded the farmers' hard work, while dividing land equitably.
Ladejinsky was derided as a communist by American conservatives, who (disastrously) opposed land reforms in Latin America. But in fact Georgism was a vaccine against communism.
Some of rich people's riches comes from hard work and ingenuity; some comes from luck. Luck is like a natural resource - it's something humans receive instead of creating. So try to divide it equally.
If we define Georgism as a system that rewards effort/ingenuity but not luck/plunder, then call me a Georgist!
Any suggestion I could make ("humanism"?) would be cheesy, which is why it'll take a manifesto to really make a name stick. Someone needs to write a book...