By definition, Christianity is a knowledgable religion. Bible faith is a knowledgable faith. It is knowable. This is no small statement in modern Christianity. Knowledgable and knowable involves the intellect. Therefore theology is crucial because without an intellectual theology then faith is impossible; because faith is in a living Person and apart from revelation concerning Christ faith is unattainable. Mysticism is not an option nor will mysticism ever attain Biblical faith. Mysticism ultimately generates belief in your experience.
Machine wrote concerning this trend in 1925, almost 100 years ago. Seek to renew your mind with the Word of Christ, not with your imaginations and experiences.
The depreciation of the intellect, with the exaltation in the place of it of the feelings or of the will, is, we think, a basic fact in modern life, which is rapidly leading to a condition in which men neither know anything nor care anything about the doctrinal content of the Christian religion, and in which there is in general a lamentable intellectual decline. (Machen, J. Gresham. What is Faith?, 28)
But if theology be thus abandoned, or rather if (to ease the transition) it be merely the symbolic expression of religious experience, what is to be put in its place? Two answers to this question may perhaps be distinguished in the religious life of the present day. In the first place, there is mysticism; and in the second place, there is a kind of neo-positivism.
Mysticism unquestionably is the natural result of the anti-intellectual tendency which now prevails; for mysticism is the consistent exaltation of experience at the expense of thought. But in actual practice mysticism is seldom consistent; indeed it cannot possibly be consistent if it seeks to explain itself to the world. The experience upon which it is based, or in which it consists, is said to be ineffable; yet mystics love to talk about that experience all the same. (ibid, 33)