The phrase "are unsuitable" could be replaced with a variety of synonyms depending on the context. If referring to something that is not the right choice for a specific purpose, alternative phrases could include "are inappropriate," "are inadequate," or "are ill-suited." If describing something that is unpleasant or unacceptable, synonyms such as "are unfitting," "are disagreeable," or "are unacceptable" may be more appropriate. When describing someone's skills or abilities, options such as "are unqualified," "are incompetent," or "are unsuited" may be used. The choice of synonym will depend on the specific situation and the intended tone or emphasis of the language used.