I was thinking about the phrase ‘The pot calling the kettle black’. It comes from a time where cooking was done over open fires and cookware would become visibly ashy. (Fun fact: It first appears and was perhaps coined by Cervantes in Don Quixote!)
What are some other idioms that have lost their literal connection to time? What would be a good modern replacement?
I think that the phrase is so old that the difference between a pot and a kettle might have been fairly subtle differences in shape, but both would be black cast iron.
Which is nowhere near as profound as your interpretation.