I'm thinking of a phrase that describes someone with a holier-than-thou attitude while being unaware (or not addressing) that they are, in fact, no better. For example, a person who vapes criticizing a smoker for ruining their lungs. Maybe something along the lines of 'the blind leading the blind,' but with more connotations of self-righteousness and hypocrisy. Does a word/phrase like this exist?
The usual phrase is the pot calling the kettle black.
The origin is historical when pots and kettles were hung above kitchen fires. Both the kettle and the pot would become covered in soot.
"The pot calling the kettle black" is a proverbial idiom that may be of Spanish origin, of which English versions began to appear in the first half of the 17th century. The idiom is glossed in the original sources as being used by a person who is guilty of the very thing of which he accuses another and is thus an example of psychological projection, or hypocrisy.
Also Cambridge Dictionary
Under self- in the OED:
1631 R. Bolton Instr. Right Comf. Affl. Consciences 392 Never to bee found in the affections of a Self-ignorant, Selfe-confident, unhumbled Pharisie.
1745 J. Mason Treat. Self-knowl. i. i. 8 Condemning others for the very Crimes we ourselves are guilty of,..which a self-ignorant Man is very apt to do.
The only headword definition I can find is for the noun:
Ignorance of one's own character, powers, and limitations.
Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co. Farlex.
Self-ignorant is not rare in print, for example:
Few fall that are afraid of falling: but the self-ignorant and self-confident are careless of their way, and it is they that fall Richard Baxter; On the Mischiefs of Self-ignorance (1828)
While I am not so self-ignorant that I fail to realize that I would like to go myself, I do not quite realize that I am unlikely to indulge this desire without some additional reason for doing so. George Ladd; What Can I Know? (1914)
The poem's title, says Simpson, cryptically restates these alternative possibilities: 'self-unseeing' can mean both 'self-ignorant' and 'unselfconscious'... G. Blank and M. Louis; Influence and Resistance in Nineteenth-Centery English Poetry (1994)
To lie to oneself is to condemn oneself to self-ignorance, a blight on the inner being of a person either from an ethical or a psychiatric point of view. James Drane; Becoming a Good Doctor (1998)
The Symposium, Sanday argues, is both a kind of warning for human beings about how not to live a self-ignorant or self-evasive life and a philosophical recapitulation of the Delphic command which reveals just how demanding it is. James Ambury and Andy German; Knowledge and Ignorance of Self in Platonic Philosophy (2019)
Someone who is aware of their own shortcoming might be described as self-aware:
Having conscious knowledge of one's own character and feelings.
‘we're self-aware enough to know we're making mistakes’
Thesaurus.com gives the following antonyms for self-aware:
clueless; oblivious; uninformed; unsophisticated; foolhardy; foolish; ignorant; thoughtless.
Of those, clueless, oblivious and unsophisticated might be the best fit, but...
It doesn’t give self-unaware, which I’ve used and seen used on occasion. That particular word may need to be written with the negation highlighted, self-unaware, to draw the reader to the intended meaning via self-aware, although most of Twitter’s real-life examples don’t bother.