Can't we have both? In fact, I think it is imperative in a soul's journey and development to both individuate and conjoin.
I don't agree that it's "imperative... to both individuate and conjoin." Each person's path is a unique one, and that's the point of individuation, to find YOUR OWN TRUE PATH, your own way of being in this reality, as well as your own way of connecting to spirit.
Some people are clearly a lot more extraverted than others. They thrive from being actively involved in events out in the world, and are much more socially inclined. Whether that means that they will have an easier time conjoining with others on a spiritual level is questionable though, because extraverts are generally very easily bored with introspection, and would rather be DOING than BEING. They tend to have a lot of friends, but don't tend to develop intimate relationships very easily, mainly because they are seldom just "too busy" for that. They may have a deep unspoken loyalty and love for their intimates, but because they are not good at (or don't have time for) expressing it, that can lead to some turmoil in their close relationships.
Introverts are much more comfortable with their inner reality. They can spend a lot of time alone, content to be with themselves, and their own thoughts, feelings, intuitions. They often feel drained from being around people too much or too long, and prefer to know just a few people well. In my experience, introverts are usually more genuinely creative, because it's easier (and more natural) for them to tune in to their own inner musings and come up with something original from those experiences. Introverted intuitive types are the ones who are known for their mystical tendencies, their ability to see "the whole picture," regarding the Oneness of soul. But they tend to be rather ungrounded, and have such a hard time with practical reality and especially with money, that they can live a very unbalanced life, if they don't learn how to take care of practical business.
Of course there is nobody who is 100% introverted or extraverted, but people do have inclinations one way or the other. According to Jung, it's the INFERIOR FUNCTION--the weakest one that leads one towards individuation. One of the more common motifs in fairytales has to do with a king (the dominant function), who has three sons.Two of the sons will be fairly well adapted, and know how to perform their duties in a way that is met with approval by the king and all who reside in the kingdom. And then there will be a third son, who is a bit of a goofball, and is known for his strange, sometimes literally backward way of doing things. That's the one von Franz likens to the inferior function. Inevitably, there will be some big crisis in the kingdom, and at that point all three of the sons will be asked to take up the challenge of slaying a monster, or rescuing a princess from a dark castle, or solving what seems to be an unsolvable riddle. As it always turns out, the two well adapted sons fail at the tasks, and the goofball son ends up being the one who succeeds-- kills the beast, saves the princess, and rescues the kingdom from ruin.
"We're not on our journey to save the world but to save ourselves. But in doing that you save the world. The influence of a vital person vitalizes." (Joseph Campbell) I definitely agree with that.