GD&T is the only tool we have with which to manage machine part geometry perfectly. In particular, it’s the only tool we have with which to impose truly functional limits of imperfection on machine part features and actually guarantee assembly and operation prior to drawing release.
GD&T is difficult to get right even though it is very logical. What does “right” mean? Right means several things, but mainly that it imposes achievable, fully function based and only necessary permissible limits of imperfection using absolutely syntactically correct code.