It does take time, but when you launch a product that's missing basic features (like a shopping cart, something almost every online store in existence has) you tell on yourself to your customers, and let them know they're not a priority.

I don't disagree that Steam's feature rich platform makes it hard to compete with on that level... but for fuck's sake, at least try a little bit. Especially if your first move is to say they're unfairly gaming the market by... providing something people want.