Discussions about appropriate travel attire are a perennial topic here on FlyerTalk. Pretty much always they devolve into straw-man arguments about "People can't tell me not to wear comfortable clothing." Usually this is spurred on by some recent travel magazine article waxing nostalgic about the days when everyone dressed up in public and dress codes were enforced.
The interesting thing is, as far as travel magazine articles waxing nostalgic go, the one cited by OP here is fairly benign. Pilar Guzmán describes what travel attire was like years ago while simultaneously acknowledging that it is not like that today. She doesn't ask for a return to the past. All she's saying is be comfortable but not slobby.