What Kṛṣṇa says, they will not accept it. Kṛṣṇa says, sarva-dharmān parityajya mām ekaṁ śaraṇam: (BG 18.66) "Only take to Kṛṣṇa consciousness." Sarva-dharmān. Because any dharma which is not approved by the Supreme Lord Kṛṣṇa, that is not dharma. Dharmaṁ tu sākṣād bhagavat-praṇītam (SB 6.3.19). A human being or a demigod or very exalted person cannot manufacture dharma. That is not possible. Real dharma is given by the Supreme Personality of Godhead Kṛṣṇa, and that real dharma is stated in the Bhagavad-gītā: sarva-dharmān parityajya mām ekaṁ śaraṇaṁ vraja (BG 18.66). "Just surrender unto me." This is real dharma. Surrender to Kṛṣṇa and follow His instruction; your life will be perfect. Because you follow the perfect instruction, therefore you are also perfect. Simple process. To become perfect, we have to follow the perfect instruction.
So in the Bhagavad-gītā there is perfect instruction. And if we take it as it is and follow it, then we become perfect.