"Just because we have already progressed beyond a given philosophy doesn't mean it wasn't a critical step on the path to where we are today. And such philosophies are still important in areas that are less advanced or regress."This is a vitally important point that is so often missed by many and it's crucial to almost evey field of endeavor that we encounter.
Let me give you what is probably the quintessential example by way of an analogy. To understand the science of mechanics to the extent that we do nowadays, we first had to absorb and then digest Newton's Mechanics through its various iterative refinements, Lagrangian and Hamiltonian Mechanics etc., and it took us several hundred years before we had a sufficient understanding of its implications that it became possible for us to make the next great leap forward in our thinking. When we arrived there we very quickly developed both Quantum Mechanics (1900) and Special Relatively (1905) and from whence we further progressed through to General Relativity (1915) and beyond.
However, this was by no means a simple matter, for along the way we had to make new physical observations such as
the Michelson-Morley experiment and to develop new and quite different mathematics, for without both such progress would have been impossible. The mathematics alone took a torturously winding path involving completely new ideas and concepts. Diverse developments such as William Rowan Hamilton's Hamiltonian and quaternions, Ricci-Curbastro's curvature, Hilbert's 'Space', Minkowski space and others were absolute prerequisites for the new physics of the early 20th Century, it couldn't have progressed without them.
Sure, that's a long-winded analogy to reach my point but it illustrates how complicated and convoluted it can be to make progress in any endeavor - and that includes both philosophy and political science.
Like Newton, Hobbes's world is, in many respects, very different from our world of today. No matter how brilliant a person of that era was, they simply would not have been able evolve ideas past a certain point as the underlying theoretical infrastructure for him or her to do so was not yet in place.
Newton for instance, wouldn't have been able to progress his ideas forward unless he'd had experiamental data from the Michelson-Morley experiment as well as access to the new mathematics. Moreover, even if by come brilliant deduction, Newton had stumbled onto the idea of conducting such a experiment, then there's a good chance that the limited resolution of the technology of his day would not have provided sufficient accuracy for him to come to the correct conclusion. OK, let's say he had succeeded, then in the absence of new mathematics he'd then be forever left pondering the result sans arriving at any definitive conclusion.
This is why we still need to study Plato, Pythagoras as well as other great thinkers from different eras, for without them we don't have sufficient wherewithal to put everything into proper perspective.
Whilst today we can reject some of their ideas as having less relevance, others are still surprisingly modern and they are often the bedrock foundations from which we've progressed forward.
(For instance, in Book I of Plato's Republic where in a forum Socrates raises the question 'what is justice' and then formally debates the proposition with the sophist Thrasymachus, I reckon is damn hard to beat. The way in which Socrates weaves the development and logical progression of his arguments to the point where he not only ultimately renders the sophist's view worthless but also is able to change the sophist's mind to his view is nothing short of wonderful. It's a debate with logical argument that's almost without parallel. Even if one were to disagree with some of the conclusions in Plato's Republic, and given the passage of nearly 2400 years since it was written, that's not unexpected (especially so for some ideas that emerge in the latter books), it nevertheless still holds intrinsic value that makes it well worth reading.)
Thus, some 371 years on since the Leviathan, it is very easy to be critical of some of Hobbes's ideas - and that's absolutely fine - that is, so long as we do not forget that the zeigest in which he was immersed was very different to our own. Not only should we consider this fact rigorously but also we should factor it into our analysis of Hobbes's book.