The ascetic
sādhanā
, explained in the previous two verses, can lead to
ātma jñāna
(knowledge of the self).  But
brahma jñāna
(knowledge of God) requires the grace of God, which comes through devotion.  The words
sarva loka maheśhwaram
mean “Sovereign Lord of all the worlds,” and
suhṛidaṁ sarva-bhūtānāṁ
means “benevolent well-wisher of all living beings.”  In this way, He emphasizes that the ascetic path too is consummated in surrender to God, with the knowledge that the Supreme Lord is the enjoyer of all austerities and sacrifices.  Jagadguru Shree Kripaluji Maharaj has put this very nicely
hari kā viyogī jīva govind rādhe, sañcho yog soī jo hari se milāde
(Rādhā Govind Geet)
“The soul is disconnected from God since eternity.  True Yog is that which unites the soul with the Lord.”  Hence, no system of Yog is complete without the inclusion of bhakti.
In His “Song of God,” Shree Krishna beautifully includes all the genuine paths of spiritual practice, but each time, at the end He qualifies them by stating that success in these paths also requires bhakti.  For example, He uses this system of presentation in verses 6.46-47, 8.22, 11.53-54, 18.54-55, etc.  Here too, Shree Krishna ends the topic revealing the necessity of devotion.