Maybe we should add readability assessment task, too?

There had been both meaningful neural and non-neural approaches to this task. The linguistic features developed in this field can often be transferred to the other areas of text classification.

We shouldn't add this task inside text classification hence readability assessment tends to focus on "measuring" the difficulty of a text. Similar classification prediction models (SVM, HAN, etc.) are frequently used in readability assessment but I believe that the goal is different.