[sarora27]

Former Magento Cloud team member here.

Most ecomm businesses are more complex than connecting a front end to a payments gateway. Generally requires multiple complex systems (Product Management System, Order Management System, CRM, etc) to work together seamlessly. This is where platforms like Shopify or Magento are really valuable. They give you all the pieces you need to build your business w/o needing to reinvent the wheel.

[nullsense]

Don't forget inventory management, warehouse management, shipping etc.

Often platforms do a little of these themselves but lots of businesses have needs that require them to use specialised solutions that handle those aspects of their business better than Shopify does as each is a complex domain in its own right.