How can one be in an intimate relationship yet be non-attached to their partner? The only way I can see that work is if they loved their partner equally to everyone else, with unconditional love (which is indeed our fundamental goal). But then what would be the point of being in a relationship? In this transitory world, is there even a point in pursuing human love? I’m struggling to see how any intimate relationship can have a positive impact on the spiritual path, as it is still an attachment.
Intimate relationships can be powerful aids to spiritual growth — if we go about them in a spiritual way: not to pursue human (egoic) love but to learn unconditional love, which as you noted, means loving everyone equally. While sincerely enjoying the deep, human friendship of an intimate relationship, always keep in mind that deeper purpose. The relationship can be, in part, a “gym” for your heart: a setting in which you can learn true non-attachment and unconditional love. Those qualities are much harder to develop outside of a close relationship, because we won’t have to deal with relationship issues at such “close quarters.”
So don’t avoid intimate relationships on the grounds that they are transitory, because everything in this world is transitory — including you and me! Rather, if you are in — or come to be in — a close relationship, be in it wisely, above all as a way to grow spiritually.
I highly recommend Swami Kriyananda’s book, Self-Expansion Through Marriage, in which he explores these ideas in detail and in highly practical ways.