There is no universal Internet-wide sender reputation number. Receiving providers evaluate their own signals and policies.
Useful operational signals include complaint rates, invalid recipients, sudden volume changes, authentication, history, recipient engagement where a provider uses it, known abuse, and the reputation of domains and sending infrastructure.
Focus on causes
If placement drops, avoid random DNS changes. Establish which receivers are affected, compare traffic before and after the change, inspect bounces and complaints, and verify that the same infrastructure and authentication are still being used.