I am definitely guilty of looking for a TL;DR

In the context of social media, this isn't really the same problem of not wanting to or being able to read longer stuff in general. There are countless screeds from any number of sources that you wouldn't want to waste your time going through (not saying the above poster is one of them), so getting a general sense of a longer post is an important skill.

Being able to work through edited prose in detail is also important, but remember that it's very different from what we all encounter online. In the immortal words of someone who probably wasn't Twain or Pascal, "I did not have time to write a shorter letter."