Sarva-dharmān means there are so many system of religion. But any system of religion, if it does not lead you to the platform of devotional service to the Supreme Personality of Godhead, that is defective. Therefore Bhāgavata says, sa vai puṁsāṁ paro dharmo yato bhaktir adhokṣaje (SB 1.2.6). That is first class system of religion.
What is that? Which teaches one how to become unalloyed, unflinching devotee of the Supreme Personality of Godhead. That is first-class. All others, they are defective. Sometimes they are described as cheating. Like in the beginning of the Śrīmad-Bhāgavatam it is said dharmaḥ projjhita-kaitavo 'tra (SB 1.1.2). Kaitava means cheating. So anything going in the name of religion, but it is cheating, that is rejected here. Dharmaḥ projjhita. Projjhita means prakṛṣṭa-rūpeṇa ujjhita. Just like when you sweep with a broomstick, you cleanse all the dust, throw away, similarly, in the Śrīmad-Bhāgavatam, in the beginning it is said that cheating type of religious system is completely swept away. Dharmaḥ projjhita-kaitavo 'tra paramo nirmatsarāṇām (SB 1.1.2).