replaced it with state landlordism and political allocation which equally involves rent seeking behavior
False. Housing in the Soviet Union was rented at maintenance cost prices, and on average costed 3% of the monthly income. This is not rent-seeking behaviour.
In both Soviet Union and China land was collectivized, which removed incentives for land use, agricultural output fell and a famine followed
Terrible analysis. The 1930-1933 Soviet famine was caused by economic and productive disadjusting due to the need for extremely fast industrialization, combined with drought and retaliation by landlords. After the initial drive for industrialization, agricultural output rose immensely due to usage of modern agricultural techniques and land reform, and hunger was actually eliminated. The big hunger episode in China was similarly not created by lack of incentive to cultivate the land, but by an ecological catastrophe caused by misguided anti-plague campaigns that eliminated a key part of the ecosystem in a time and society before ecological sciences were developed. Similarly, agricultural output rose rapidly after that and hunger was permanently eliminated. You can compare the exponential rises in life expectancy in the USSR and China after those episodes with similarly developed countries like Brazil or India respectively, and you'll find that this land reform and industrialization drive saved hundreds of millions of lives.
Scholars have argued this is because economists like John Bates Clark (foundational to the still dominant school of economics: the neoclassical school) was paid by landlord lobby to make “land, capital and labor” into “capital and labor”.
That's the biggest problem with Georgism. Policy is not something you can apply based on which one is ideologically better theoretically (which I don't even agree Georgism is), and Georgism, not doing any class analysis, doesn't provide answer to the most basic question: why would the landlords in power allow us to tax them? And if they don't, how do we force them?
Socialism having had mass movements and success in expropriating the land from landowners is not a coincidence: since Marx and Engels put forward scientific socialism and Lenin advanced the idea of the vanguard party and of revolutionary tactics, the only revolutions in the world have been socialist.
We don't need to fund anything with taxes, that's outdated classic economics. Modern monetary theory has proven otherwise. We don't need taxes to fund things, states can create unlimited amounts of currency, the whole "this is funded by taxes" is simply not true. Taxes work primarily for three purposes: removing money from the economy to prevent inflation, imposing obligations denominated in a certain currency to enforce usage of said currency, and discouraging certain behaviors.
If the whole point of taxing is not to pay for anything, and the whole reason is simply to disincentivize landlordism, georgism simply offers no advantages over collective land ownership and public decisions over land usage. Wanna build housing? Build it. Wanna build schools? Build them. Wanna have a park? Have it. The obsession with taxation is outdated once we've found out that taxes aren't paying for anything and we can have arbitrary amounts of currency created with the purpose of funding whatever projects we collectively decide. In this manner, Georgism is obsolete.