Observability is not about pretty dashboards but about quickly answering real questions: why did response times get worse? Which service is causing the error? Is the problem tied to a deploy, a customer or an external integration? Common tools are Prometheus, Grafana, OpenTelemetry and Datadog.
In a good platform, observability is part of the golden path: every new service is born with logs, metrics and alerts — before its first incident, not after.