There is no evidence that people have a higher
overall level of education before entering the workforce over time.
Rather, people know a different set of skills and accumulate a different body of knowledge. It is only if we define "education" as the degree of knowledge in the body of subjects we teach today that one can say people in the past had less of it. But that's only because we have discarded the many bodies of knowledge an educated person needed to have in the past.
For example, one can laugh and say that to earn a doctorate in mathematics during the renaissance you'd need to know algebra only to the level of solving a cubic equation. However you are missing all the archaic geometric ruler and compass constructions, evaluation of various infinite series, and deep knowledge of Latin, Greek, French, German texts, mastery of rhetoric, music theory, and other topics that few learn today. So it is not true that a mathematician of the present could waltz in and get a Doctorate in Philosophy in medieval Paris. He would probably get quickly thrown out for failing to master the many various scholastic topics that were required of a PhD in that time period, and which no one learns today.
As another example, a new worker in 1800 might be expected to know how to deliver a calf, fix a fence, shod a horse, make homemade preserves, skin a rabbit, set a broken bone, paint a barn, as well as know Greek, geography, history, recite the speeches of Cicero, translate the Odes of Horace, navigate the seas by an astrolabe, stain a bookcase, identify the key flood valleys of Europe and know which animals could be hunted in which part of the year in various European forests, or know the biographies of German princes, etc. But you are correct, they wouldn't have MS Office skills or know how to create a webapp.
Once you move past "hunter-gatherer", you very quickly run into complex societies with their own historically developed bodies of knowledge that require lifetime learning, whether that means learning the seasons and details about planting crops and irrigating fields, dealing with pests, where to dig a well, how to tan leather, etc - or whether that means something else, it is still a vast body of knowledge that takes decades to master. The point is, wherever a society is technologically, it will choose different areas to train its workers, and omit other areas that are no longer needed. But how many resources does a society need to train its workers? If that number keeps growing, then there is something wrong with the society.