TL/DR has always meant that when written in response to a wall of text. If you’re going to post a wall of text, you need to accept that the VAST majority of people will not read it, and include a summary. Convention has evolved that the poster can highlight a summary of their wall of text themselves (and avoid a snarky “TL/DR” comment from others) by the poster highlighting the summary with their own TL/DR notation.

TL/DR: If people are throwing TLDR at you, you need to practice summarizing, rather than comeback quips.

It literally always meant that?

It stands for "too long; didn't read."