Your channel is your brand, and that means sticking with your niche. As you're putting together a content plan, consider how each piece fits into the narrative of your channel. If videos you produce rank highly within your niche, YouTube will be able to target audiences that are interested in similar content—and your channel's overall visibility will increase. Stay focused with the content you create, and as your viewership increases, so will your subscriber numbers.
I do not think this is how most people use YouTube. YouTube videos are more like blog posts, and fit more effectively into the niche of content marketing. Sure, people will comment—but they do so in a manner similar to how they comment on blog posts. They come to view and digest videos, not necessarily share their thoughts about the day. Because of this, you should approach YouTube as content marketing instead of social media marketing.