Then, only strong social and emotional bonding of leader with employees can keep the employees happy and engaged.

It is a good question Pankaj. I agree that leaders are important but in actual, it is the system or establishment of a company that runs it. Yes, a single person/leader could have its influence in the company to accomplish success but it is also the collective work that makes it possible. So, I don't think the departure of a single leader can't make a company out of the run. Big companies have strong departments that can lead the company without personnel. I hope you would understand my point.

You raised a valid point but in my opinion, the importance of employee engagement has increased a lot in the last decades because of the competition. Actually, it is the competition that teaches the employers about the significance of employee engagement.

You are absolutely right that positive words or appreciation can improve the employee retention at the workplace. However, you can't ignore other factors like satisfaction, good leadership and a clear vision in this regard. I found this article https://www.millforbusiness.com/why-is-employee-engagement-important/ very informative regarding employee engagement. I hope it would help to explore more secrets to engaging employees.