The problem with pursuing unity is that it actually creates a duality with those who don't join the unity. Furthermore, to achieve unity from two or more diverse and unique entities requires each of them to either sacrifice their differences, or to assimilate the differences of the others.
For these reasons, "harmony" is preferred to "unity", and "wholeness" is preferred to "oneness".
Rabbi Ted Falcon puts it this way:
"Our task is not to exclude others nor to deny our differences, but to find the core teachings that unite us."
United, but not a Unity. Integrated to create a whole which is greater than the sum of its parts; diverse and in harmony.
Upon examination of any ancestral tree, or the history and very design of life itself, we see that the unities are in the past, and diversity is the future. Acknowledging past unity, or the present tiny unity, is rather effortless, and concentrating on it is a distraction, looking backward. Our opportunity and challenge, our focus and effort, looking and moving forward, is not to attempt to reunify, but to harmonize.