Chan or Zen Buddhism we have to regard in two basic forms: specific spiritual exercises taught by Buddhist monks since the time of the Buddha, and Zen (禪) the lineal institution (宗) which bears the marks of having been finally mythologized during the Song dynasty, what most of us recognize as the Golden Age of Zen, which is more fiction than historical fact and helped to further the fortunes of the Zen lineage (禪宗).
What both have in common is the belief that the primogenitor was Gautama the Buddha; and that any spiritually competent person could realize what Gautama realized whereby he became awakened or Buddha. This belief is the root of all Buddhist traditions from Theravada to Tibetan Dzogchen.
Buddhism, in this respect, is not without genuine awakened individuals insofar as Buddhism is not just about holding on to various beliefs but, more importantly, whether or not such beliefs actually obtain through certain mystical experiences. In Zen, this experience would be kenshō, that is, intuitively seeing one’s true nature. During the time of the Buddha this would be nirvāṇa, or in Pali, nibbāna. This is not any kind of intellectual knowledge, i.e., any kind of conceptual or linguistic knowledge. It is instead, intuitive knowledge which is the immediate apprehension of ultimate reality which is unconditioned. Nor can it, in anyway, be visited by the senses. It falls under the general category of mysticism.
How this all rests with modern thought and the modern individual depends a great deal upon how encumbered the individual is by the various modern dogmas which depend on a kind of loyalty to ideological materialism, if not ‘scientism’ which has been socially engineered into the individual since their birth.
If this is the kind of person that Zen Buddhism has to teach, it will likely not be successful without, itself, being revised to tally with the demands of materialism and its various forms. In other words, the modern individual wants his or her Zen Buddhism to deny the personal realization of true reality whether it be Buddha-nature, or an unconditioned, non-empty reality called the One Mind.
Buddhism, but more so Zen, is standing at a crossroad. If Buddhism, in general, and with it Zen, is to survive outside of the Asian community it will have to get stronger in its polemics against a culture of materialism and also stronger in its apologetics, making a much stronger case for rebirth and karma than it has in the past. You don't adapt to a culture by giving up your core principles and tenets—by ignoring the Buddha's enlightenment.