One of the worst things about Environment variables among others discussed here is the implicit and opaque nature of them. Majority of applications rely on them in the *nix world. Even if more explicit and obvious ways of configuration files or remote services (consul/etcd, et al.) and command line arguments are supported env vars are traditionally supported as well.
But as mentioned in the article it is just a global hashmap that can be cloned and extended for child processes. Maybe in 1979 it was a good design decision. Today it sometimes hurts.
For example, kubernetes by default literally pollutes the container’s environment with so-called service links. And you will have fun time debugging a broken application if any of those “default” env vars conflict with the env vars that your app might expect to see.
https://kubernetes.io/docs/tutorials/services/connect-applic...
They are ubiquitous and we are living in the world of neo-conservatism in IT where legacy corner cuts are treated as a standard and never challenged (hello /bin, /usr/bin, /lib, /usr/lib)[0]