And to give you another example, look at how many people bricked their computers because Linux decided EFI variables were files. You can blame the vendors all you want, but the reality is this would not have happened (and, mind you, it would have been INTUITIVE to every damn user) if the OS was sane and just let people use efibootmgr instead of treating every bit and its mother as files. Just because you have a gun doesn't mean you HAVE to try shooting youself, you know? That holds even if the manufacturer was supposed to have put a safety lock on the trigger, by the way. Sometimes some things just don't make sense, if that makes sense.
"The way it works is useful?"! When was the last time you found it useful to delete something like /dev/null via command line? And how many poor people do you think have screwed up their systems and had to reboot because they deleted not-really-files by accident? Do you think the two numbers are even comparable if the first one isn't outright zero?
It literally doesn't make any sense whatsoever for many of these devices to behave like physical files, e.g. be deletable or whatnot. Yes there is an exception to every nonsense like this, so yes, some devices do make sense as files, but you completely miss the point when you ignore the widespread nonsense and justify it with the exceptions.
Your complaint is with the semantics of the particular file. There's no reason why files in /dev need be deletable using unlink. That's an historical artifact, and one that's being rectified.
"Everything is a file" is about reducing most operations to 4 very abstract operations--open, read, write, and close. The latter three take handles, and it's only the former that takes a path. But you're conflating the details of the underlying filesystem implementation with the relevant abstraction--being a file implies that it's part of an easily addressable, hierarchical namespace. Being a file doesn't imply it needs to be deletable. unlink/remove is not part of the core abstraction. But they are hints that the abstraction is a little more leaky than people let on. Instantiating and destroying the addressable character of a file poses difficult questions regarding what the proper semantics should be, though historically they're deletable simply because using major/minor device nodes sitting atop the regular persistent storage filesystem was the simplest and most obvious implementation at the time.