Does second hand let me try before buying? Do they allow me to return? If they fail either of these conditions it's already a non-starter.

It's also entirely unrealistic to expect people to cough up mega dollars for single pieces of clothing when they can build a whole outfit from fast fashion for the same price as a single "good" piece of clothing.

Quality is relative. If you wash carefully and rotate clothing/outfits properly, a fast fashion piece can last a year plus with ease. If you abuse your clothing by tossing it in the wash after a single wear or use insane temps and drying cycle, it's going to get rekt. That's called common sense.

Do you think everybody makes six figures a year? Do you think only people who make more than 50k a year are allowed to own stylish clothing?

It's down to economics and convenience, and when it comes down to the wire, I will sooner run and buy an outfit from HM or ZARA then sit at home and wonder about the suffering of planet earth and the destruction of the environment. Me not buying a single piece of fast fashion will do absolutely nothing to save the earth, it will only inconvenience me and cost me money. The business will continue as usual.