The Vaisnavas are by far the greatest philosophers in the world, and the greatest among them was Srila Jiva Gosvami Prabhu, whose philosophy was again presented less than four hundred years later by Srila Bhaktisiddhanta Sarasvati Thakura Maharaja. Therefore one must know very well that Vaisnava philosophers are not sentimentalists or cheap devotees like the sahajiyas. All the Vaisnava acaryas were vastly learned scholars who understood Vedanta philosophy fully, for unless one knows Vedanta philosophy he cannot be an acarya. To be accepted as an acarya among Indian transcendentalists who follow the Vedic principles, one must become a vastly learned scholar in Vedanta philosophy, either by studying it or hearing it.
(Sri Caitanya Caritamrta------1:7:102------purport).

Unfortunately, in this Age of Kali there are many mundane persons in the dress of Vaisnavas, and Srila Bhaktivinoda Thakura has described them as disciples of Kali. He says, kali-cela. He indicates that there is another Vaisnava, a pseudo Vaisnava with tilaka on his nose and kanthi beads around his neck. Such a pseudo Vaisnava associates with money and women and is jealous of successful Vaisnavas. Although passing for a Vaisnava, his only business is earning money in the dress of a Vaisnava. Bhaktivinoda Thakura therefore says that such a pseudo Vaisnava is not a Vaisnava at all but a disciple of Kali-yuga. A disciple of Kali cannot become an acarya by the decision of some high-court. Mundane votes have no jurisdiction to elect a Vaisnava acarya. A Vaisnava acarya is self-effulgent, and there is no need for any court judgment. A false acarya may try to override a Vaisnava by a high-court decision, but Bhaktivinoda Thakura says that he is nothing but a disciple of Kali-yuga.
(Sri Caitanya Caritamrta------2:1:220------purport).

One's devotional attitude increases in the association of a Vaisnava:
tandera carana sevi bhakta-sane vasa
janame janame haya, ei abhilasa
By his personal example, Narottama dasa Thakura stresses that a devotee must always remember to please his predecessor acarya. The Gosvamis are represented by one's spiritual master. One cannot be an acarya (spiritual master) without following strictly in the disciplic succession of the acaryas. One who is actually serious about advancing in devotional service should desire only to satisfy the previous acaryas. Ei chaya gosani yara, mui tara dasa. One should always think of oneself as a servant of the servant of the acaryas, and thinking this, one should live in the society of Vaisnavas [Cc. Madhya 13.80].
(Sri Caitanya Caritamrta------2:19:156------purport).

Srila Bhaktisiddhanta Sarasvati Thakura explains that unless one is directly empowered by the causeless mercy of Krsna, one cannot become the spiritual master of the entire world (jagad-guru). One cannot become an acarya simply by mental speculation. The true acarya presents Krsna to everyone by preaching the holy name of the Lord throughout the world. Thus the conditioned souls, purified by chanting the holy name, are liberated from the blazing fire of material existence. In this way, spiritual benefit grows increasingly full, like the waxing moon in the sky. The true acarya, the spiritual master of the entire world, must be considered an incarnation of Krsna's mercy. Indeed, he is personally embracing Krsna. He is therefore the spiritual master of all the varnas (brahmana, ksatriya, vaisya and sudra) and all the asramas (brahmacarya, grhastha, vanaprastha and sannyasa). Since he is understood to be the most advanced devotee, he is called paramahamsa-thakura. Thakura is a title of honor offered to the paramahamsa. Therefore one who acts as an acarya, directly presenting Lord Krsna by spreading His name and fame, is also to be called paramahamsa-thakura.
(Sri Caitanya Caritamrta------3:7:12------purport).