Not to be a jerk, but IMO this is a good example of why not to build your own greenfield e-commerce solution for your B2C idea. They were a "a New York based fashion retail startup that served consumers in South Asian countries to shop from luxury western brands" so it's entirely unclear why their own in-house e-commerce platform would be anywhere near enough of a value-add to be worth the investment.

Skimming the code it looks like mostly an overengineered CRUD/SPA with a lot of non-DRY code, possibly some security issues, and no obvious major game changer that would have made it worth building in the first place. And building it would drastically slow down ability to iterate on the actual business proposition of selling stuff, down to e.g. the HTML for customer emails hard-coded into JavaScript.

I sorta see this as the inverse of the no technical founder problem - it's the solely technical founder problem, where you're supposed to be focused on selling luxury fashion to South Asian consumers but that's boring and you'd rather be a cool startup writing your own e-commerce app using "MongoDB, Express.js, Vue.js, Node.js, Mongoose ORM, Redis", etc. Like seeing a nail and deciding to build a hammer factory from scratch to supply yourself with a single hammer.

There are companies doing millions of dollars per day in sales on Shopify or similar platforms. You should at least be at a significant fraction of that or doing something extremely weird before you consider DIY.