Why are you surprised? Europe has 700 million people. Think of the average construction worker you know, do you think they could read and correctly summarize any moderately complex article? Think an article about inflation or evolution or heat pumps or investment funds, etc.
Fairly sure that in most countries the average person reads less than 1 book per year, so half of the population reads less than that. I know people who haven't read a book since highschool, when they were forced to.
https://worldpopulationreview.com/country-rankings/average-b...
The Average Briton allegedly reads 15 books per year. I assume its self reported and poorly sampled. Otherwise its very hard to believe (and variance between countries seems way too high) but stats like this (especially more subjective ones like functional literacy) are usually not very useful on their own.