I’ve personally dived around secrets handling in the container world and let me tell you, 95% of the cases that you listed is basically pointing a cannon to a fly 
Using our context, tools you’ve linked address one issue you will likely never see: secret rotation.
And, in the end, the container has the value either in an environment variable or in a directory (you can do it with podman using –secret, for example), so if container is hacked, you still will have access to everything inside the container.
Tools like this are used (and even not at all due to the widespread of built-in solutions in orchestration softwares) when you have to develop something on kubernetes or something like that. Not the case here 