There's always been propriety code installed on systems, who knows what that big Oracle database is actually doing?

Are these sysadmins actually looking through the open source code that they're compiling to make sure that there isn't a security flaw in plain sight?

With Docker you can get containers maintained by a trusted source, as a sysadmin you don't have to deal with all the hassle of upgrading things, you can just replace the container with the latest version. With Docker content trust the containers are signed.

There have always been cowboys out there and that has nothing to do with the tech stack.