It's still useful in EC2 (or any other VM-based environments) and Docker containers, as long as you can install the necessary packages (if they are not installed by default). Because after all, there are "servers" underneath, even for the serverless apps, I suppose.

It's definitely harder for apps running in Lambda because we may not have access to the underlying OS. In such case, I kind of fallback to using the application level observability tools like Pyroscope (https://pyroscope.io). It doesn't always work for all the cases and have some overheads/set up but it's still better than flying and more useful than the Cloud Provider's provided metrics.