I think fast fashion is a behaviour of the individual consumer rather than an attribute of a particular brand though.

I suspect wherever you buy the clothes from they likely come from the same sweatshops and factories in Asia just with different markup.

Many people say Zara is fast fashion, yet I sit in the Zara clothes that have lasted me 2-3 years. We are fortunate to be able to produce high quality clothing incredibly cheaply due to the wonders of modern manufacturing and the brutal exploitation of foreign labour - yet that won't stop people throwing it in the bin to get the next shiny thing an 'influencer' has shilled.