Please explain how we are to practically identify "idiomatic, standard code that a slightly above average developer would plausibly write." Or is it some Goldi

Please explain how we are to practically identify "idiomatic, standard code that a slightly above average developer would plausibly write." Or is it some Goldilocks not-unoptimised not-too-optimised I'll-know-it-when-I-see-it wishful-thinking thing?