db.serverStatus() provides a high level aggregate of command, inserts, updates etc. that occur on a system. This information is transient (ie. reset when the mongod re-starts) but provide a valuable insight on the running system.
However, the aggregation looses the details of where the operations are occuring, for example that the reads are to Collection X in DB Y, the updates are happening to Collection A on DB B etc.
Provide lower level metrics down to the collection level, for example
Getting better insight into the running system will help to diagnose issues more accurately.