For me, "TL;DR" inevitably implies a certain laziness. If a person really means, "I tried to understand this but I'm not getting it", maybe they could say that.
Given that the top reply to this post is a copy and paste from the first paragraph of the about page, I could see why people suspect the querent did not work very hard before posting, and so values their own time more than that of other people here. That might not be true, but I think it's on the asker to make that clearer, not the readers to guess.
Then that would have been a good thing to say. If you say you didn't read something when you actually did, you can't blame people for taking you at your word.
Given that the top reply to this post is a copy and paste from the first paragraph of the about page, I could see why people suspect the querent did not work very hard before posting, and so values their own time more than that of other people here. That might not be true, but I think it's on the asker to make that clearer, not the readers to guess.