A small, boring alert system wins
The best alert is specific enough to act on at 03:00 and quiet enough to trust at noon.
Alerting is a communication system. It should move a useful signal from a production system to the person who can change the outcome.
Keep the first layer small: symptoms, not every cause; ownership, not a broadcast channel; and a runbook link that starts with the next safe action.
When an alert cannot answer who is needed, what is broken, and what to do first, it belongs in a dashboard or an experiment, not on a pager.