That isn’t to say that categorical distinctions don’t matter. As a philosopher, that would be an untenable (read: incredibly stupid) position for me to take. It is, though, to say two things, one a basic principle of common sense, and the other a disciplinary question.
1). There’s absolutely no way we can know which of our distinctions will or will not have significance for the history of knowledge.
To give a totally random example, during and immediately after Hegel’s life, there was a famous split among his disciplines between the “Young Hegelians” (generally liberal) and the “Old Hegelians” (generally conservative). Anybody interested in German philosophy in 1850 would have immediately known the difference; today, I would probably say that this distinction doesn’t make an actual conceptual difference to anyone who isn’t specifically a scholar not only of Hegel but of Hegel’s influence. On the other hand, Avicenna’s distinction between “essence” and “existence” is very much at the heart of contemporary debates about ontology, even though it’s several centuries older than Hegel.
2). As Coke Talk rightly points out, undergraduates tend to be very invested in institutional and disciplinary distinctions. When I was a sophomore, I would have been incensed had anyone suggested I was a structuralist rather than a post-structuralist. Nowadays, I could give less of a shit how you label me as long as you take the time to actually listen to what I say.
As I’ve often noted, Spinoza distinguishes concepts that have a substantial basis (either in essence or in existence) and concepts which have a purely ideational basis (in the Short Treatise he calls these “Beings of the Mind”). The more different objects you join together under a single distinction, the less adequate or substantial that distinction will be and the more it will be all in your head, because it won’t correspond to an actually existing entity. As Derrida’s work has relentlessly demonstrated, any distinction that divides literary or theoretical periods into broad divisions, or which makes unilateral distinctions between genres or theoretical perspectives will be almost entirely provisional and imaginary.
In the Posterior Analytics, the Topics, and the Rhetoric, Aristotle draws an important disciplinary distinction between deduction and dialectic. Whereas a deduction is intended to prove, a dialectic is intended to convince. This has an important implication for the production of discourse: Anything which is to be proven must begin from valid principles; the whole idea of Aristotelian deduction is that no matter how implausible, unusual, or counter-intuitive the deduction, the deductive method itself assures the legitimacy of any conclusion which is both true and valid. Dialectic, on the other hand, intends to convince its hearers. As such, the point of departure is not a valid premise, but an acceptable one: Aristotle explicitly notes that if the first premise is not one which is acceptable to the listener, the entire argument will fail to convince them.
The point of all this is that in making conceptual distinctions, the question is rarely one of “correctness.” In fact, I’m going to go ahead and formulate this as a general principle: The more ideational/the less substantial any given distinction, the less “truth” is can possibly have, because it doesn’t correspond to any actually existing entity against which its “truth” can be measured. To put it more bluntly: in making a distinction (for example, between “post-feminism” and “3rd-wave feminism”) the question is not which term is more correct but rather what are you trying to achieve with this distinction? If the answer is “to convince someone,” your primary concern should be the clarity of your distinction, not its “validity.”