Of course, but in the end everything is an abstraction. You can use functional reactive programming to expose a stateful API, for example; there’s nothing wrong

Of course, but in the end everything is an abstraction. You can use functional reactive programming to expose a stateful API, for example; there’s nothing wrong with that. And on the other end of the spectrum, if you go low level enough you realize that everything is stateful in the machine, so you will need to build (or already have) functional abstractions on top of that. Bottom line, it’s almost impossible to have a single paradigm on all levels of your stack.