What you're referring to has been a thing for a very long time and exist outside of the US.
The Nikes you get at a department store have always been terrible compared to what you get at Foot Locker for example. Nike won't even allow certain sneakers to be sold depending on the level they judge the store to be.
The Ralph Lauren flagship store in Tokyo or NYC will generally have a better selection than the department store. A Macy's in Chicago will have a far better selection of a brand than a Macy's in a mid tier suburb. In college, I went to a mall serving an extremely rural community and a major college, and nearly everything in the casual section of the department store was extremely cheap and camo.
Its just market segmentation.
Online, the clothing brands I buy from directly tend to be of the quality I expect. Buying a polo from Amazon will be just as much of a crap shoot as buying from Temu, but the online store will generally have the quality shirt you've been buying.