Your premise that one can simply “choose” to change chassidus is where you are mistaken.
Perhaps not change, but one *can* choose if he is not in one at all. I know that if you walk into a Satmar shul, a Chabad shul, a Breslov shul and others, they will not turn you away and say “you can’t belong to this chassidus because you’re yeshivish.”
The Wolf