Counterfeits are one issue, but brands have to accept that they cannot control distribution channels as they have in the past. Companies don't like to have their products showcased against similar products, but that's inevitable. Margins will shrink, and they'll just have to compete more on quality, value and reliability. In the end, the consumer benefits. The only solution would be to severely restrict what it means to own a product in a legal sense, which would be very harmful to consumers who value ability to re-sell and donate clothing.
[0] https://www.wsj.com/articles/how-nike-resisted-amazons-domin... (paywall)