The main distinction between systems languages (e.g. C, C++, Zig) and non-systems languages is that in a systems language you can interface directly with the OS

The main distinction between systems languages (e.g. C, C++, Zig) and non-systems languages is that in a systems language you can interface directly with the OS/hardware or at least a very lightweight runtime. If you need to talk in a language other than what the hardware speaks, you would need a layer inbetween the programmer and the hardware. Systems programming languages are what we use to create abstractions for non-systems languages, in particular runtimes. E.g. Java's JVM is written in C/C++. A defining characteristic of a systems programming language is that 99% of the runtime could be written in said systems programming language (maybe with some assmebly in the last 1% for system calls). That isn't possible in Java for example, you can't have a garbage collector that needs a functional garbage collector to exectute. Systems languages compile directly to machine code, and have enough features that can be used to interface with drivers and hardware. Systems languages have a very close association between what you write and how the computer works under the hood. Deviating from that von neuman model to make it do whatever you want is possible, but then it's no longer a systems programming language.