The acharya’s duty is to find the means by which devotees may render service.

“Śrī Caitanya Mahāprabhu, in His teachings to Rūpa Gosvāmī, said:

brahmāṇḍa bhramite kona bhāgyavān jīva
guru-kṛṣṇa-prasāde pāya bhakti-latā-bīja
(Cc. Madhya 19.151)

One can achieve the seed of bhakti-latā, devotional service, by the mercy of guru and Kṛṣṇa. The duty of the guru is to find the means, according to the time, the circumstances and the candidate, by which one can be induced to render devotional service, which Kṛṣṇa accepts from a candidate who wants to be successful in going back home, back to Godhead. After wandering throughout the universe, a fortunate person within this material world seeks shelter of such a guru, or ācārya, who trains the devotee in the suitable ways to render service according to the circumstances so that the Supreme Personality of Godhead will accept the service. This makes it easier for the candidate to reach the ultimate destination. The ācārya’s duty, therefore, is to find the means by which devotees may render service according to references from śāstra. Rūpa Gosvāmī, for example, in order to help subsequent devotees, published such devotional books as Bhakti-rasāmṛta-sindhu. Thus it is the duty of the ācārya to publish books that will help future candidates take up the method of service and become eligible to return home, back to Godhead, by the mercy of the Lord. In Kṛṣṇa consciousness movement, this same path is being prescribed and followed. Thus the devotees have been advised to refrain from four sinful activities — illicit sex, intoxication, meat-eating and gambling — and to chant sixteen rounds a day. These are bona fide instructions. Because in the Western countries constant chanting is not possible, one should not artificially imitate Haridāsa Ṭhākura, but should follow this method. Kṛṣṇa will accept a devotee who strictly follows the regulative principles and the method prescribed in the various books and literatures published by the authorities. The ācārya gives the suitable method for crossing the ocean of nescience by accepting the boat of the Lord’s lotus feet, and if this method is strictly followed, the followers will ultimately reach the destination, by the grace of the Lord. This method is called ācārya sampradāya. It is therefore said, sampradāya-vihīnā ye mantrās te niṣphalā matāḥ (Padma Purāṇa). The ācārya sampradāya is strictly bona fide. Therefore one must accept the ācārya sampradāya; otherwise one’s endeavor will be futile.”

Source: A.C. Bhaktivedanta Swami Prabhupada (2014 edition), “Srimad Bhagavatam”, Tenth Canto, Chapter 2 – Text 31