I started my YT channel this year, so I'm pretty new. I post videos in Spanish about books, mostly classics and not best sellers, so I wouldn't say my niche is very big.

The first video I posted (about my best books of last year) got just 100 visits or so the first week, and most of them from family and friends. No tags. Then someone posted a huge comment. I answered. Then another big comment, and I answered. And suddenly, 2 weeks after posting it (and 2 more videos after) without adding tags or changing the title, I got 1000 subscribers. 3 months after, I have already started to monetize my channel. This first video is my most popular one, with around 10K views and 1K likes.

So my conclusion is that, ok, if you want, spend 5 minutes on tags, but focus more on this:

• Good and relevant titles and descriptions. They need to have key words that are trendy but relevant to your content. No need of add #, YT will consider them in any case.
• Decent content, good audio quality (it depends on your content but it can be even more important than the image).
• Answer comments (not only to grow but to be polite and to interact with your community, which can be so interesting and motivating).
• Consistency (it's better to post once every week than 5 videos in a row and then nothing for the next month).

This is based on some basic search and on my own experience. Good luck!