ubiquitin,
Interesting OP. These are some of my thoughts in no particular order.
1. Halacha seems to me to be a system of applied morality. Hashem created a universe with moral principles, some of which we understand, some we do not, and gave us the Torah as a means to apply those principles in our lives.
2. I disagree that “much of Yahdus has machlokisism involved”; I think that for the vast majority of halacha there is broad agreement, and the disagreements come over a small subset of finer points.
3. Even when given a machlokes, I see a big difference between machlokes and moral relativity. Ashenazim and Separdim wrap their tefillin differently, but both sides agree that tefillin should be worn, and that it consists of black boxes with pesukim inside, leather straps, etc. Nobody (frum at least) is coming along and saying, “we need new tefillin for the 21st Century!”