The Kingdom of Godhead is not a myth but it is situated far beyond the boundary of the material cosmos and one can know it by the process of devotional service only.
Pure devotional service is the satisfying activity for the soul. So Lord Caitanya was specifically preaching pure devotional service, this was his unique contribution. Even in the history of whole vedic culture it was very rare to find someone who is preaching pure devotional service, other than Narada-muni and some acharyas. Lord Caitanya was very strict he wanted his followers to maintain that integrity of preaching only pure devotional service. When some of his followers visit other people who are not preaching pure devotional service, he would abandon them.
Although karma, jnana and yoga are discussed in Bhagavad-gita, the only purpose is to inform us of Krishna’s greatness and engage us in His devotional service.
Lecture on "Understanding Krishna through Bhagavad Gita" – Salem – 8th Nov'06
Loving devotional service to the Lord begins with hearing about the Lord.
Srimad Bhagavatam 1.7.7,
When we expose ourselves to severe vaisnava-aparadha, it is like pulling our devotional creeper out from the root. It doesn't get the nourishment then we systematically dry out, then we lose the taste for chanting, reading, deity worship, book distribution, what could be worse! We lose devotional service ultimately.
Devotional service is so simple, but devotees because of their material inclinations make it complicated.