Two miles from my house there’s an awesome charity store that supports the Montana Rescue Mission, which provides services to the homeless. If you have something like this where you live (and I don’t think Goodwill is one), you should really start donating to it AND shopping there.
There are so many upsides: The profits go to charity instead of sweatshop operators; you’re helping people to recycle their unwanted items, which keeps them out of the trash; there is a huge and ever-changing variety of items, which makes finding something good really fun; and you’re reducing the demand for new items to be manufactured. That means that even if you’re a minimalist, you can feel fairly good about any money you spend and any items you bring home. And if you decide the thing you bought is not right for you after all, you can just donate it back to the very same store you bought it from, and all it costs you is a small donation to charity.
I guess the downside is that you can’t always find something you need right when you need it, but I would consider that less a downside and more a “slight inconvenience of the type most ‘consumers’ should really learn to deal with.”