There are many reasons to boycott fast fashions companies like H&M, Monki, Only, Forever 21, ZARA etc. Horrible working conditions (sometimes child labor) and destructive, wasteful production methods in far away countries is problematic in a plethora of humanitarian and environmental ways.
Fast fashion means clothing that doesn’t last. There is nothing more wasteful than constantly buying new clothes and I try to get almost all of my outfits from thrift stores.
There are however a few companies that focus on sustainable, vegan clothing. I like TWOTHIRDS; they use organic and recycled materials and produce everything in Europe. A lot of their clothes are vegan, which is awesome. By taking the time to invest in quality, I feel like I am saving time, money, and myself from the guilt that comes from going to H&M, etc. five times a year.