Comment by wavemode

Diving into flame graphs being worthwhile for optimization, assumes that your workload is CPU-bound. Most business software does not have such workloads, and rather (as you yourself have noted) spend most of their time waiting for I/O (database, network, filesystem, etc).

And so, (as you again have noted), your best bet is to just use plain old logging and tracing (like what datadog provides) to find out where the waiting is happening.