Best sustainable fashion marketplace for solo founders

There are roughly 15-25 dedicated sustainable fashion marketplaces globally (Etsy, Depop, Vestiaire Collective, The RealReal, etc.), plus another 40+ niche platforms targeting eco-conscious brands. The common failure pattern: most platforms either cater to established brands with inventory depth, charge unsustainable commission rates (15-25%), or require technical setup that alienates non-technical founders. Solo founders specifically struggle with three things—discovery (how do customers find them among thousands?), payment processing costs eating margins, and lack of community/mentorship. The real gap isn't in the marketplace itself; it's in the *infrastructure layer* around it: bundled services like micro-fulfillment, shared logistics, pre-vetted supplier networks, and simplified accounting that treat sustainability metrics as a selling feature rather than an afterthought. A new entrant should either (1) focus on a hyper-specific subcategory (e.g., sustainable swimwear, regenerative textile startups) to own discovery, (2) build a B2B wholesale model for solo makers to sell in bulk to retailers, or (3) create a co-op structure where founders share fulfillment and marketing costs, flipping the commission model upside down.