Ecommerce breaks in a lot of places. Compliance, advertising, logistics, cash tied up in stock, and sometimes the plan itself. Most of the job is working out which one is actually costing you this quarter, and having the nerve to say what to stop doing about the rest.
For five of those years I was also researching AI and machine learning at IIM Ahmedabad, running client accounts alongside it, until I left in 2019 to run the agency full time. The research shaped how I set targets, per SKU rather than one number across a channel. The rest I learned on the accounts.