"Conservative" literally means "averse to change" so of course they will always unify around a set of traditional beliefs.

The Democratic party has a harder time "unifying" because it's more accepting of change, but there is a wide spectrum of tolerance around how much and when people adapt to rapidly changing social and fiscal policies. Ultimately I think there is unification, but there's lag time for everyone to catch up and be on the same wavelength; a lag time of years, sometimes decades. This gives the perception of a disorganized party, but realistically it's more complicated than that.