They may be dead, but we still have some amazing alternative OS’s that exist that, as far as I’m aware, are still being updated. First thing that came to my mind was AROS ( Amiga Research Operating System that had to change the name to AROS Research Operating System ).
I personally don’t use it since I don’t use Amiga software, but it’s still really cool. Under no circumstances would I recommend it as a daily driver because any software based around Amiga is purely hobby at this point, but it’s still cool to check out.
The only time I have ever heard the word copacetic and only reason I know it exists is because of a song that probably only dinosaurs and hipsters listen to anymore: Bound For The Floor.
Other than that, I’ve never heard it used in any context. So I’mma agree that it’s definitely an old person word ( or a pretentious “I’m BeTtEr ThAn YoU” kinda word ).