I think tradition can and does play a role in informing jurisprudence to a degree. Of course we are free to discard it as it becomes irrelevant in a progressive society.
A swing on the progressive scale should not be a mindless discarding of tradition, however, and that sort of attitude probably does not help the cause. It is quite possible that in certain areas of law, it is true that an "ideal" may exist, or if not an ideal, then a situation that is "better" or "preferred" to other situations. It could be that the traditional situation is the better one in some cases. BUT if you want to make that argument, then you need to bolster it with something other than "this is how it has always been."
For example, in the area of family law, and particularly adoption, it may very well be true that a two-parent home is preferred. You can probably find multiple, credible sociological studies to reinforce that fact. So in that sense, perhaps tradition is symbiotic with the law, but it does not mean that it is the only or exclusive way. And the fact that the traditional family set up has its benefits does not mean that we are relying on tradition to shape our law, we are merely admitting that social studies indicate that this may be the case in this one example.
Anyway, I have rambled, but just as tradition shouldn't shape our law, it doesn't mean that it doesn't inform it (surely it does, anybody who's read case law knows as much).
