Philosophy is hard to understand. There is not a standard set of things one needs to know in order to “know philosophy,” in the same way that there is such a set of things for chemistry, biology, or math. This is due to the fact that philosophy is a field that is shaped basically differently from these other fields.
The difference is that philosophy is not a field of knowledge. It is about having a grasp of things in general, rather than about having a grasp of some specific things. This is not a different degree of challenge, but a different kind of challenge. If one had knowledge of every specific thing, this would not amount to a grasp of things in general.
Much of the difficulty of communicating about philosophy arises from language. Language is not an adequate tool for conveying philosophical ideas. This means that philosophical writing strongly tends towards the obscure. The greatest abilities of clear expression do not eliminate this problem completely.
That said, the challenge of thinking clearly about philosophy is a different one. And thinking clearly must come before communicating clearly. Philosophy does not have very many fundamental problems; and all of the problems are highly interconnected. So it is possible to have a clear and general grasp of philosophical issues.
Incidentally, if one has this understanding, then other philosophers will usually make sense. This suggests that the fundamental challenge is not speaking clearly, but thinking clearly. If one can think clearly about philosophy, then the language of philosophy will be intelligible.
Some of the challenges in thinking clearly about philosophy also seem to arise from language. Language is part of our mechanism of thought, and in philosophy, linguistic anomalies can result in cognitive anomalies. A person can easily be bewildered by a word.
This type of confusion comes in many forms, and Wittgenstein analyzed this phenomenon in detail in his later works. I will content myself with giving one example.
I once had a discussion with a friend where he wondered whether or not he existed. He had begun with the word “I,” and, without clarifying what “I” meant, he proceeded to ask whether or not he existed. He could not figure out whether or not he existed because he did not know what he was talking about.
For my own part, I no longer run into these confusions over language. I think the reason for this is that when I think about philosophy, I no longer think in words; I think in visualizations and abstract relationships.
I think that a clear grasp of philosophy is something that one must learn for oneself. The way to get it is to spend a lot of time thinking about philosophy. Everybody who does this will end up with a different angle on philosophy; they will have their own philosophical personality, so to speak. That is because the nature of philosophical problems is that they do not have logically tidy resolutions, like the problems of math and science.