The beaten-down e-commerce stock isn't as cheap as it looks.Down 80% year to date,Shopify's (SHOP-3.36%)decline has far outpaced that of theNasdaq Compositeindex, which has "only" fallen 33% in the same period. Thebeleaguered e-commerce platformhasn't held up well after the COVID-19 pandemic. And while its unique business model gives it an economic moat, slowing growth and a high valuation should give investors pause.What went wrong for ShopifyFounded in 2004 and going public in 2015, Shopify is an e-commerce platform designed to help small businesses create customized online stores where they can sell items both online and in-person. It differentiates itself from large third-party online marketplaces such asAmazon by focusing on merchants instead of the end consumer.Like most e-