Śrīla Bhaktisiddhānta Sarasvatī Ṭhākura has given a detailed explanation of the four rituals mentioned here, namely agnihotra, darśa, paurṇamāsa and cāturmāsya. The conclusion is that everyone should simply chant Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare/ Hare Rāma, Hare Rāma, Rāma Rāma, Hare Hare and avoid the difficult entanglement of Vedic ritualistic ceremonies. If one neither chants Hare Kṛṣṇa nor performs such rituals, one certainly becomes a pāṣaṇḍī, an atheistic fool.