When we visualize an ideal person, we spontaneously imagine them to be beautiful. There is nothing wrong with this: we simply want what is inside them to be reflected on the outside, as it should be in an ideal world of transparent truth. What would be shallow is letting someone's good looks cause us to lower our standards regarding their personality, as this would mean that we have ceased to seek ideal looks to match ideal personality and instead have begun to let good looks compensate for bad personality. But we can be vigilant against this without lowering our standards regarding their looks either. On the contrary, it is by further raising our standards for looks that we best safeguard against this, since this makes it harder for them to awe us with their looks in the first place.
Another angle to consider is that whereas personality can be feigned, looks (until recently with the advent of cosmetic surgery) could not be. And even when sincere, personality could well have been shaped by that person's unique life experiences, whereas looks are more likely to reflect heritable traits. Thus selecting for looks first could be a more efficient way to preliminarily filter out most carriers of heritable traits that we don't want.
One way in which I do not care about good looks is if someone originally beautiful (and with good personality) became disfigured as a result of an accident (fire/acid/etc.). I would still feel the same about them as I felt prior to their disfigurement.