Reading the original work is of course its own experience and can be worthwhile for that experience. But it shouldn't be necessary in order to understand the philosophical ideas and arguments, just like for example it absolutely isn't necessary to read Einstein's original papers to understand and discuss relativity. It can give some flavor, or a better understanding of the historical development, but that is non-essential for the actual subject matter. In philosophy, however, there is a sentiment that you have to trace the historical development and debates to be able to understand the subject matter. Whereas the actual philosophical matters of fact, the truths that we are trying to come up with in philosophy, surely shouldn't inherently depend on the happenstances of the historical course of philosophical debate.