"The box is not important, what's important is what's inside the box." Are there any idioms or poems that can sum it up?

Buy a casket and return a pearl

[Pronunciation][mǎi dú huán zhū]

[Explanation] casket: wooden box; pearl: pearl. Bought the wooden box and returned the pearl. It is a metaphor for having no vision and making improper choices.

[Source] Song Dynasty Cheng Yi's "Collecting Handwriting with Fang Yuan": "There are many people who treat classics today; however, everyone buys a coffin and returns it as a pearl."

[Example] When reading a book, you must absorb the essence, and don't do ~ stupid things.

[Similar meaning] Putting the cart before the horse and putting the cart before the horse

[Antonym] Eliminating the rough and extracting the essence