Joke aside, there are ways to compute a "readability score" for any block of text. This is useful for document writers that need to target particular grade-levels for their docs (eg driving manual is "8th grade"). https://readability-score.com/
The readability score is based only on the lengths of words, which I guess is something, but it's not a very good proxy for when you learn the word. The frequency of the word is a much better thing to measure.
