Are personality theories just pseudoscience?

It has long been believed that people can't change their personalities, which are largely stable and inherited. According to most personality type theories, the individual's type is inborn and does not change. However, I believe that this belief says more about the psychoanalysists themselves than it does the people they are analysing. How can any human being possibly believe that there is any comparison between our personality at three years of age and our personality as an adult? I find it rather frightening that there are actually professionals in the field of psychology that appear to be of this belief. I am of the opinion that If you believe you cannot change, then you will not change. 

I will be arguing that there is no generally agreed upon definition of personality, so personality theories are just pseudoscience.

Personality is the characteristic sets of behaviours, cognitions, and emotional patterns that are formed from biological and environmental factors, and largely shared by all human beings.

Personality can also change over time, even from one moment to the next. It is not set in stone, and there are no big five personality traits which a human being can be judged on.