From a technical standpoint you need to get off monolithic platforms like Shopify and BigCommerce, and even Salesforce and Oracle Commerce Cloud. These platforms stifle growth and present limitations for scaling.

What you need is something called a headless, mircroservices-based, API-first e-commerce architecture. A mouthful, I know. Fortunately there is some OSS and SaaS that makes adopting it easy. For OSS check out https://www.vendure.io/; for SaaS check out https://www.fabric.inc

The reason Amazon is able to scale so quickly and add new channels and features so quickly is because of their innovative technology and approach to technology management (e.g. two pizza teams).