If bananas were a central part of anarchist ideology and, through decades of discussion and theory, we came to a more holistic and useful conception of what constitutes a banana than the common understanding of what a banana is, I would argue in favor of using the more distinct definition. But the state is also infinitely more complicated than a banana. It's character has changed over time, often progressing in ways that past anarchists have predicted. The fact that a hundred year old conception of the state still has legs shows that not only is it accurate, but useful. You could define so many horizontal societies as states using the common definition. If we're trying to build a society distinct and separate from what currently exists, shouldn't our language reflect that? It's important to distinct, concrete markers for progress in our struggles. And the abolition of the modern state is among the top of the list in matters of importance.

Just because we can peacefully coexist and even work with the state apparatus for a time doesn't mean we don't seek it's elimination. If we're calling our end goal by the same name as the thing we wish to eliminate, it only serves to create confusion. What's the point of saying "the state is our enemy, we seek to recreate the state but minus all of the things that most people would consider functions of the state?"

Language can also be prefigurative, and part of that is using terms held in common among our group in the way we understand them. It's far easier to mold this facet of the world we wish to change if we're not immediately contradicting ourselves and confusing others. Even if you went through the route of focusing strictly on power dynamics and heirarchy without mentioning the state. Eventually it's going to come up, people are going to ask if we want to get rid of the state/government. What do you say? "We don't want to get rid of the state, we want to turn it into the state but one that's completely unrecognizable as a state to the average person"?