Gaining high engagement rates on YouTube is absolutely essential for building your community of subscribers. Your most enthusiastic subscribers will watch most, if not all, your new videos, plus often they will be there to like them and give you support. Engaging with them is very important; you should always aim to get feedback from them straight after uploading a new video. Comments mean engagement, and when people see that you have engagement under your videos, they will more likely to get engaged with your videos.