Are you talking about knock-offs or actual reproductions?

Well, some will say there is little difference. So I am asking a broad question, I realize.

Generally, knock-offs are simplified versions in order to facilitate lower costs and faster production, and are therefore not reproductions.  Couture and Designer Label are usually rather expensive to manufacture (relative to mass market) and include more intricate detailing and more expensive, better quality fabrics.  Often times the designers' garments (what comes down the runway) are used for inspiration and trend development.

You should also consider historic fashion influences on modern design--whether it is just for inspiration or "retro".

I was told that there is nothing is brand new design under the Sun. We can do for product development will be focused on target consumer to adjust the needs and wants of the target consumesr.

I think, very very few designers come with completely new ideas. Most of the designers copy the design somehow or others. For an example. if you put some traditional Chinese or Indian style in US, for them it is innovative, but actually it is not. Although I'm not a garment design person, but being a textile engineer and attaching with garment industry I realize this truth.

https://www.researchgate.net/publication/305887180_Beyond_the_Border_Yellow_Goes_International

Article Beyond the Border: Yellow Goes International