1. Map the product or idea being built to those who will use it. Present it, get users feelings on it, if it is viable and needed. Throughout development, gather continuous feedback by demoing, shadowing, and adapting to new feedback. Plan and execute a launch, watch for snags, provide support and solutions to users.
2. Communicate gathered feedback to engineering, and do so with an understanding of where the project is engineering-wise, where it is going, what needs to change. Give engineering the "why. Convey the priority of everything the project needs vs what it has and what is being worked on.
Repeat this feedback loop.
But most of them seem to think they can operate entirely in document-land and just crank out roadmap docs and keep stakeholder alignment via endless check-ins and nagging. They are doing a "project manager" job instead.