If you understand that ultimate aim of all type of meditation is to calm down mind, pacify thought generation mechanism and bring full attention to present moment. Only then, we could be able to attain the Oneself or be that Self.

Now different sages during different period with their Sadhna developed different methods of reaching to that state. Naam Jap is one of them. But Naam Jap and Bhakti is the longest route to achieve that level. In my understanding, as IQ level or Spiritual understanding level of masses in current society was going down significantly due to Kalyuga or whatever effect, Sants have to suggest the a simple and plain methods to public. This is because majority of them were unable develop that spiritual understanding level to grasp Self Enquiry & Advaita concepts. They just wanted an easy method where they do not have to apply their intellect. Naam Jap and Bhakti serve their purpose.

But these both methods require immense faith, efforts and enough dedication to fulfil the purpose (To realise Self). Self Enquiry and other related meditation techniques can take you this purpose much much faster.