[sdnguyen90]

Expanding on what other people have said with some anecdotes:

Most developers who don't have operational experience of a ecommerce business will recommend some kind of open source cart. If they're in the WordPress community they'll recommend Woocommerce. If they're used to building web apps they'll recommend something built on top of their framework of choice.

Almost everyone who has experience working on a successful ecommerce business will tell you to use Shopify. It has all the basic tools you need to run a successful store. If your store is a failure on Shopify, then it would probably be a multitude worse on a custom built cart.

As stated in other comments, the actual cart is a cost center in a ecommerce business. There are stores using themes with minimal modifications doing millions in sales. On the contrary, you could have the most well built site and still have no sales.

If you want to put your technological skills to use, use it on things that generate traffic like content or marketing.