Here's what rhymes with shallowness.

Consider these alternatives

superficiality / personality youthfulness / usefulness unfamiliarity / therapy frivolity / quality narrowness / mellowness immaturity / insecurity naivete / day banality / personality hypocrisies / crises inexperience / experience ineffectiveness / effectiveness artificiality / personality rebelliousness / gregariousness vacuity / continuity inaccessibility / ability