Philosophers throw around author-turned-into-adjective terms like Kantian, Hegelian, Aristotelian, Humean, Hobbesian, Benthamite, and so forth as frustratingly vague substitutions for the actual ideas meant. (Kant wrote a lot, which part are you referring to?) Intro biology and political science textbooks are all organized similarly with more or less the same content, while different intro philosophy textbooks often seem like they're covering different fields. (E.g. one author believes the main questions in philosophy are metaphysics and logic, while another gives most space to ethics and religion.) Why? Because there is no widely agreed-upon of what the really important issues in philosophy even are. (Just look at continental vs. analytic philosophy.) So in the absence of any kind of consensus organization/taxonomy and terminology to go with that, it all just reverts to... original texts and author surnames. It's organized by history.
(And even when modern thinkers try to come up with conceptual-sounding names, it turns into a confusing mess. Try to remember which one is "contractualism" and which one is "contractarianism". Or is there a difference between "morals" and "ethics"? Or why do some writers call it "utilitarianism" while others call it "consequentialism"? When you say "resentment", which author's usage of "ressentiment" are you actually referring to? I usually know the answers to these questions, but they sure are confusing when you're learning it as an undergrad. It's actually clearer if you say "Hobbesian" rather than "contractarian", or "Nietszchean" so I can understand which type of "resentment".)
Learning the history of philosophy is helpful... but it does seem somewhat strange that while you can learn math or biology without needing to learn the history or ever read a single "original historical text"... you can't learn philosophy without learning its history. And so that certainly leads to the question... should you be able to? Would that improve the study of philosophy?