One of my classmates has worked with several of these, starting with Myntra, moving on to Jabong, Hopscotch and Lenskart (by Flipkart) before moving on to becoming an EIR at some VC firm.
According to him, most of these are operating at hair-trigger margins and it is the funding that is keeping them going, waiting for the day when they can either increase prices and still win or make enough volume to become profitable. The main wildcard is the internet penetration and the transportation structures in tier II and tier III cities - if they can manage deliveries at scale for cheaper costs to enough people, it should work out for them. Otherwise they will all lose to local stores anyway which have decades of inventory management skills.
Personally I think the real opportunity is building the tech to enable these local stores that you mention. Selling tech is much more scalable and higher margin and you take advantage of the existing delivery networks + customer relationships.
You would still have to eat costs for a few years, but long term I think those are the teams that will build the really significant companies.