Complexity is always something we consider - in every team I've ever worked on. DBA's always talk about the complexity of the data. Dev's always talk about the complexity of the code base. And UI Dev's and Designers always talk about the complexity of the UI.
No one understands the cost of complexity better than engineers. We understand the increase in the likelihood of bugs, or the increase in maintenance and refactoring costs. We understanding that making a UI complex means users may have difficulty learning how to complete a task and get frustrated, and we understand the costs of those frustrations.
I'm not sure why this person thinks engineers and product managers don't understand the cost of complexity. In my personal experience, it's always been business and sales people who don't understand how adding a shiny new feature could be harmful in any way.