The history of the world and economics is far more nuanced than rich people hoarding wealth. Wealth is the economy, it's created from systems. The feudal system in the medieval age was relatively poor at generating wealth. A series of technological and intellectual developments began to rapidly increase in the 1400s that culminated in the modern era, including especially the printing press.
But in the 1300s serfdom was still the norm in Europe. Serfs did not get paid and so the Plague made no difference except 2/3 of the population died. Serfdom would last another several hundred years after the plague, and in some countries all the way to the 20th century.
Financialization can also make it appear wealth has increased when really nothing has happened.
If all property is “owned” by the crown and people only have various “rights” to it that can be inherited but never encumbered or sold, then there’s really no point in “valuing” the land beyond simple comparisons.
Once land can be bought and sold value appears to track it; but the land was always there.