Well, sure. But it's also exactly the contention of its proponents: that the categories represent orthogonal concerns about how we process information, but that our variation across those categories explains the larger trait distribution we experience.

My point wasn't to argue about how well they did that (not particularly), but rather that it's useful to approach issues of understanding personality in those terms at all. That's the real innovation of things like the MBTI: that we should analyze the distribution of personalities in terms of PCA, and that we should probably use a few components, rather than like 1 or 2.

Of course, we could do the actual analysis much better than the MBTI did.