This is a hard one as I am sure there are a ton of layers to unpack here. Whenever there is a question around metrics, I would first look to the customer and understand what customer pain points your product area is solving for. Then see how those needs and your business goals align, and how your specific area can help solve for that. If it is a matter of stakeholder management that is a different story, but engineering, product and design should really have shared KPIs.
The worst KPIs to commit to are the ones you can’t commit to at all. We can set targets and metrics and make dashboards, but that’s exactly what they are - targets. I recommend looking at past performance and trends within the data and setting a realistic yet aspirational target to work towards. After that, begin iterating on your target. Revisit the KPI, analyze, adjust, and communicate your findings.