Do you find that KPIs are more valuable for external reporting (looking good to other teams/management) and less valuable for your job as a PMM?
Maybe this is a better question for my team.
For me, I think it's the opposite. KPIs are valuable for me as a PMM because, through all the noise and new requests/projects that I inevitably get in a specific period of time, I can pull my head out of the weeds and make sure I'm moving towards that targeted KPI. It helps to bring measurable meaning to my work.
Due to the fact that PMMs don't have "direct impact" on key biz metrics like revenue or renewal/upsell/churn, the value perceived by other teams/management isn't always tied to a black and white number, or at least it doesn't stay there. When I've evaluated PMMs with executives in the room, they always bring a ton of anecdotal comments even and quickly move beyond hard performance ratings on paper.
I think there is an element (for all teams in an organization) of reporting on metrics to internal stakeholders as a way to promote one's self, team and work. That said, I don't think that detracts from the value of KPIs for PMM teams.
At the very least, KPIs help monitor and manage progress. As an example, looking at past launches as a benchmark for future launches - and where there is room for improvement and monitoring if new tactics improved past performance.
Good KPIs also help with prioritization and focus and ensuring the right resources are spent in the right areas based on the committed outcome.
Performance evaluation. For the business, you'll want to be able to share how your team is contributing to the performance of the business and therefore how well your team performs. But in addition to this, personally this will be something that you'll want as you progress through your career and need to advocate for yourself , especially in a leadership position.