It’s a good OP because it asks a different question. In asking a different question, it points to its own answer. It’s probably a bit difficult to see how this is so, but let’s have a go.
But first, it might be worth reiterating the point that the fact of disagreement implies an overwhelming level of agreement. Consider, if you will, how much you and I must agree is the case in order for this discussion to even be occurring. I won’t labour the point; it can be found in the many discussions of On Certainty and On the Very Idea of a Conceptual Schema.
Our disagreements are always minutiae in comparison to that about which we agree. But our disagreements are also much more interesting, so we focus on them.
Let’s next look at plumbing. There are always different ways to plumb a building. It’s not just that we might run the pipes in various different ways, but that we might put the tap and toilet in various different locations, or add or subtract a sink here or there, or choose a heat pump or instant gas. There is no simple binary of right or wrong in plumbing a building. But we can well imagine, if we employ more than one plumber, their arguing about the many wheres and hows. And yet they agree that there are pipes and taps and drains, and they agree as to the general order in which these ought to be connected.
I hope the analogy with philosophy is apparent.
There’s also the topic I took up in my thread on An approach to aesthetics . Just as no sooner is a definition of Art given than some artist will seek to undermine it, in the name of art, no sooner is a philosophy given than some philosopher will seek to undermine it, in the name of philosophy.
All this by way of pointing out that disagreement is inherent in the very act of doing philosophy.