The British Navy had a lot of ships with names that are good sounding archaic adjectives such as Indignant, Illustrious, Indomitable, Undaunted, Vivacious (https://en.wikipedia.org/wiki/List_of_ship_names_of_the_Roya...)
They also use names that seem bad choices today such as Inconstant, Inflexible and Terrible (that word changed meaning over the centuries. Originally, it meant “terror-inducing”. https://en.wikipedia.org/wiki/HMS_Terrible lists eight ships with that name, going back to 1694, so I guess that stil was the intended meaning for the one from 1944)
The word dreadful (almost certainly also a warship name) has not suffered quite such an ignominious decline but "I'm dreadfully sorry" is quite often seen in the wild.
It also reminds me of words like 'irreparable', rolls off the tongue quickly.
Now, when I hear someone use the word 'extant', especially during spoken language, I immediately think it's pretentious.