I would argue that an essay does display a level of comprehension if it is administered correctly and if the requirements are correct. My English teacher has a strict policy in regards to what you can and can't include in an essay about literature. Plot summary, which just means anything that directly states facts from the book, is forbidden. You must instead provide your own unique analysis that supports your own specific, beyond-the-text claim.
If it's an informative essay, then it's about compiling readily available information from multiple sources into a small, comprehensive package that makes the topic easier to understand than it would be by just trying to look it up. Even so, it's probably fair to say that research papers are approaching busywork.
Personally, I think it depends. Essays are by no means always pointless. They are a tool for instruction that is often mishandled.