Nitpick: a friendship is a relationship. Just not a romantic one.
I believe something similar to what you say, except I would take it a bit further: to enter into a romantic relationship without that is not only unwise, but in my estimation, impossible. Physical attraction is, pure and simple, an essential part of romance*. To be blunt, if you are considering marriage (which consideration should be present in any romantic relationship) you are expecting to eventually satisfy that person's sexual desires. And how are you going to do that properly if you are not attracted to them? If there is no actual connection, then how is the sexual aspect of your relationship going to be any more meaningful than it would be if you were just a mechanical device?
It is possible to develop physical attraction for someone with whom you do not have that initial spark. I have done so myself: I became physically attracted to a girl after initially being attracted by her intellect and sense of humor. That spark died after I later encountered some very serious flaws in her personality, but the point still stands: physical attraction can grow out of a spiritual, intellectual, or emotional attachment. But if you consider yourself to be romantically involved with someone to whom you are not physically attracted, you're fooling yourself; and if you tell them that you love them in a romantic way, you're lying to them.
So just be friends with people. If you find yourself eventually connecting in all ways (spiritual, intellectual, emotional, physical) with a woman, then consider a romantic relationship with her. If any of those things are lacking - not just physical attraction, but any - then remain simply friends, and don't worry about it any more.
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*I feel I should make an exception to that statement for true celibates (those who have no sexual desires at all). I am not willing to say that romance is out of bounds for such people, if they are satisfied with non-sexual forms of intimacy in an exclusive relationship.