Sorry to be blunt but seriously? Come on. This is like saying that the dastar should not be worn because it is not what modern people wear. Its is one of the four kakars. The kacha must be worn by a Gursikh. Its Guru's hukam. The kachera is the symbol of modesty. To control lust. One thing that this modern age needs to control. The purpose of the kacha is a lot more relevant now than it was back then.
Also what is wrong with the clothes of 'that time'? I don't understand. Women still wear salvar kamij. Men still wear kurta pajama. The banna is the clothes of the Khalsa and should be worn with honour. It looks beautiful on both men and women. It a type of clothing that is simple to make and easy to wear. Other modern cloths are provocative. (Some not all) Honestly Sikhi teaches to stand on your own feet be aware of what is right and what is wrong and think for yourself. Sikhi is not a blind faith and our Guru's never taught us to be blind.
Anyway there's no point. Do your won research first just google kachara and read why Sikhs wear it. Then think for your self. Do we need it or not?
Thank you