If Rangers were suddenly better than monks with unarmed strikes, would monks lose something in that scenario? If Paladins suddenly were better wildshapers than Druids, would Druids lose something in that scenario? Of course "taking the key identifying factors of another class" is a meaningful thing which is not happening in a vacuum but which has implications for the class whose key identifying factors they've copied.
How would you feel if Wizards could now not only do metamagic, but in some key ways do it better than sorcerers could do it?