You're correct in pointing out that Malthusians have never been correct, but there's a difference between being a Malthusian and pointing out that land is not going to become irrelevant.
Let's get some back of the envelope calculations here. At current equilibrium price, it takes about 100 million USD to build an apartment complex for 2500 families(probably the most land-efficient way to get housing) here (and my country is good at building cost effective apartment complexes.) Excluding the cost of buying land, that total cost will drop to about 70 million.
I already said that we're going to have 3 billion more people by 2050. With these 3 billion and an average family of 4 (so that population stays the same), we need housing for .75 billion families. Dividing that by 2500 gives 300,000, and multiplying that by 100 mil. USD gives 30 trillion USD. That's about 1/3 of total world production per year, and that's excluding a lot of relevant and big costs(like price elasticity of inputs for building, regulation changes, location and housing type preference, increased world demand for goods and services, etc.) Even though it's going to be paid over 30 years that's costing 1% of the total world production at very minimum and that has to come out of nowhere(you cannot simply reallocate but have to invent some way to increase production.) At GDP growth rate of about 2% for the developed world, that means you have to put at minimum about half of that growth rate into housing problem.
So far we just touched on housing. What about factories, data centers, shopping malls, roads and rails, farming complexes, mines for new resources, and other things that need land? Land is important and will still be important in the future.