How do you stop your team from obsessing over weekly signup charts?

It's so easy to get high on the dopamine of seeing signup numbers tick up every Monday morning, even when most of those users never log back in after day three. We hit a wall when we realized our massive growth spike was just filling a bucket with a hole in the bottom. Getting the team to stop caring about vanity metrics and actually fix the onboarding friction took a real mindset shift. If you've been through this, what metrics finally forced your team to wake up and focus on actual usage instead of just new signups?