There are great designers, but you could hardly invoke an artistic copyright on fashion (except for the original drawings) because fashion dresses aren’t merely artistic. The function of a dress is to be worn by a body (part). That function is therefore relatively independent from the designer’s individuality and even if a very original dress was completely “reverse engineered”, that is not to be assimilated to plagiarism, since it fulfils independent requirements of that “utensil” like keeping you warm or “decent”.

Under current laws, you could argue I suppose that fashion design is patentable in a limited way, since a dress has a function… and of course you can argue that cheap imitations of design, by deceiving the customer through the use of an unauthorized trademark are inflicting a material harm to a company and its standards of quality.