Looking at the Cultural Background
99
śruti-smṛti-purāṇādi- pañcarātra-vidhiṁ vinā aikāntikī harer bhaktir utpātāyaiva kalpate  [Bhakti-rasāmṛta-sindhu 1.2.101]
That is, without references to  śruti ,  smṛti ,  Purāṇas , and  Pañcarātras , unadulterated devotional service is never achieved. Therefore, anyone who shows a devotional ecstasy without reference to the  śāstras  [Vedic scriptures] simply creates disturbances. On the other hand, if we simply stick to the  śrutis , then we become  veda-vāda-rataḥ ,* who are not very much appreciated in the  Bhagavad-gītā .
Therefore  Bhagavad-gītā , although  smṛti , is the essence of all Vedic scripture,  sarvopaniṣado gāvaḥ .† It is just like a cow which is delivering the milk, or the essence of all the  Vedas  and  Upaniṣads , and all the  ācāryas , including Śaṅkarācārya, accept the  Bhagavad-gītā  as such. Therefore you cannot deny the authority of the  Bhagavad-gītā  because it is  smṛti ; that view is  śruti-smṛti-virodhaḥ , “in conflict with the  smṛti  and the  śruti ,” as you have correctly said.
Regarding Ānandagiri’s quotation that  kīrtanam  means  vedānta-śravaṇam praṇava-japaś ca  [“listening to the  Vedānta  and muttering  oṁ ”], the knower of  Vedānta  is Kṛṣṇa, and He is the compiler of  Vedānta . He is  veda-vit  and  vedānta-kṛt . So where is there a greater opportunity for  vedānta-śravaṇam  than to hear it from Kṛṣṇa?
Regarding the next verse, in which it is mentioned that  jñāna-yajñena  . . .  yajanto mām , the object of worship is Kṛṣṇa, as indicated by  mām  [“Me”]. The process is described in the  Īśopaniṣad , mantra 11:
vidyāṁ cāvidyāṁ ca yas tad vedobhayaṁ saha avidyayā mṛtyuṁ tīrtvā vidyayāmṛtam aśnute
“Only one who can learn the process of nescience and that of transcendental knowledge side by side can transcend the influence of repeated birth and death and enjoy the full blessings of immortality.”
*[Bg. 2.42] “Engaged in merely mouthing the words of the scriptures, but not understanding or practicing them.”
†See the fourth of Śaṅkarācārya’s meditations (page 84 of this book).