Oh yeah, I definitely think this is a myth.
In serial monogamy there is a tendency to conceptually trash our past relationships and not accept the fullness of what they were. I think this perpetuates the problem of the soul mate, because it becomes an increasingly important concept to bring the ultimate legitimacy to our final relationship. Its like an idol that grows the more partners we run through looking for the one. If people would properly contextualize their past relationships, in general they would recognize there were times in those relationships where real love did exist, and that there was a more full relationship, and had there been better leadership and / or more submissiveness the relationships would have lasted. I don't think God ever plots or undermines biblically legitimate relationships, so a failed full relationships if the fault of our fallen nature and relates to specific sins or lacks on our part. So these people really need the idea of a soul mate especially, given their experiences; and they they have a personal reason to defend it strongly.
On the other hand, in reality I believe God does sometimes pick specific people for specific people. I know in the history of the world there are monogamous male / female couples that coupled, stayed coupled exclusively, and lasted a lifetime. If they in their understanding experienced one another as soul mates, and God indeed brought them together, than is there a problem there? I would call that a God blessed marriage and given that I believe we live 1 life on earth, that goes down on the record books and would easily fit into the definition of soul mates, without necessarily condemning other good things. Subjective beauty can be deeply appreciated when we don't feel the need to force it to a God-law level.
The problem comes in when we take that personal feeling/experience attributed to soul mates and want to legally force it others without a biblical understanding, and this is what has generally happened in our culture.
Love between a man and a woman is the proper identifier of successful relationships, and none of the attributes of love is 1 Corinthians 13 necessitate a soul mate to be successfully applied. So love could exist among soul mates, and it could exist among several soul mates in a polygynous relationship, both legitimized and law abiding relationship structures.