I'm very disappointed in poem_for_your_sprog for almost understanding this point, and then immediately making the same mistake she was calling out
'I have to sort my books!' she cried,
With self-indulgent glee;
With senseless, ~~narcissistic~~ pride:
'I'm just so OCD!'
'How random, guys!' I smiled and said,
Then left without a peep -
And washed my hands until they bled,
And cried myself to sleep.
You're absolutely correct that the modern word "narcissistic" has little to do with ancient Greek mythology. See, the modern use is actually based on popular media portrayals of narcissistic personality disorder, which is why flippant use of the term is ableist.
For some reason, some people think the word's ancient Greek etymology means the modern use isn't ableist. They have some erroneous perception that modern people are speaking Greek when they say it. But as you now point out, that's ridiculous, because the word's meaning has changed over the last two thousand years. So the word has gone from being queerphobic to being ableist.
Truly, anyone who says the word is okay because of ancient history is an idiot.
This is the opposite of true. The adjective "narcissistic" has been in common usage since the late 19th century to mean the exact same thing it means today, i.e. "self-centered." The term "Narcissistic Personality Disorder" wasn't coined until 1968.
Truly, you're eager to manufacture outrage for some benign things. What's up with that
"In common use in the 19th century" is a liberal interpretation of Havelock Ellis coining the phrase "Narcissus-like" in 1898. Sure, that's the 19th century for two more years, but the actual word "narcissism" doesn't appear until 1911, and it's clearly within a psychiatric context.