Well, you definitely have to drill down. For instance I'm about to start a YouTube channel teaching YouTube, a niche already full to the max, so you may think.
But, as a avid outdoorsman, there are complications and difficulties that adventurers and outdoors types have to deal with that no one talks about in the YouTube teaching niche. So I'll start a channel dedicated to helping Outdoors YouTubers break through the noise, build a business out of something they love while helping them to avoid cringe worthiness and technophobic aspects of getting started on YouTube. (Gotta slim down that missions statement, I know; I know.)
Also my fishing channel. Is fishing saturated on YouTube? Yes, but "no one" is talking about jug fishing, cane poles, handlines and other traditional methods of fishing. My entire business has been based on the things the big boys don't bother with or just only cover via a challenge or something.
This is called niche marketing or finding a niche. It's about looking at a marketplace that is already saturated on the top end, drill down lower and lower until you find a problem, want or desire that is not being met in the marketplace, then build your YouTube channel on that.
Yes, you will have to crank out lots of videos, but also use the resources here to help you find a niche. My YouTube channel has gone through several iterations until I decided on the current format of fishing adventure "films" on the main channel and YouTube teaching on the second channel. You can do the same. You will have to experiment, but you will also have to find a niche that is not being covered by the big boys.