Metaphysics concern the big questions of existence both human and planetary. Without asking the big questions, we can never answer the little ones. Metaphysics also relates philosophy to science, which establishes relevancy for the study of philosophy. For this reason, metaphysics is still very relevant to the study of modern philosophy.
A large part of philosophy deals in "what if" instead of "because this." For that reason alone, there's no logical purpose for excluding metaphysics from the categories within the philosophical realm. While there are obviously some limits that can be taken to prevent indulging the more absurd realms of metaphysics, it shouldn't be excluded.
Since metaphysics means the "true and underlying nature of things" it's an undeniable category of philosophical discussion. In some ways metaphysics may be more relevant to finding the true underpinnings of the universe than religion and science combined. The overwhelming misunderstandings surrounding metaphysics is reason enough to keep it an acceptable, yet controversial, philosophical category of discussion.
Philosophy deals with the meaning of life on all different levels. That means that we need to include metaphysics because it can help those of us who like to ponder what life means beyond the physical experience of it. Metaphysics is a traditional form of a nontraditional curiosity that many people have and needs to be included as a philosophical discipline.
Metaphysics should be an acceptable philosophical category. Metaphysics is a branch of traditional branch of philosophy concerned with explaining the fundamental nature of being and the world that encompasses it. I think it would be a mistake to erase this category as it is the grounds that philosophy stands on.