Understanding what "Everything is was a file" means in UNIX/Linux

Understanding what "Everything is was a file" means in UNIX/Linux

This is and was a key concept of UNIX, and therefore Linux since their inception. Recently however this idea has been heavily shat upon by systemd's designers and as this blight's mission creep continues to take over more and more utterly init unrelated systems and processes, more of the "Everything is a file" simplicity and power of Linux is destroyed.

#Linux

More on Linux files and hard and soft links here:
https://www.tecmint.com/create-hard-and-symbolic-links-in-linux/#
https://www.tecmint.com/explanation-of-everything-is-a-file-and-types-of-files-in-linux/