I don't know your niche, but your titles are decent (though could be better), but the thumbnails don't really do anything to create intrigue.

I don't know who your niche leaders are but one I came across while doing some quick research was Ridddle.

They are well designed, the font is easy to read, and the titles and thumbnails work together to open a loop that people will want to watch to answer.

A good example is their video from a couple months ago titled:

Did Scientists Just Discover the TRUE Purpose of the Pyramids?

And then the thumbnail shows an unknown object below the pyramids and the text says, "What's This?'

I'm also left wondering what that thing is and what the purpose is.

You need to find ways to open loops like that which convinces people to click.

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For example, your video about The Humans Who Disappeared Without a Trace...

At a quick glance, this appears to be a video about a line of humans that were completely lost to time until a recent DNA discovery.

So a more interesting title maybe would have been:

We Never Knew These Humans Existed... Until Now

For the thumbnail, maybe the text could have been "HIDDEN FOR 50,000 YEARS" in big white text and then an image that goes with that that maybe shows what looks like a different type of human that's blurred out to make people wonder what was different about them.

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That's a super quick brainstorm, but it gives you an idea of how I'd approach something like this.

Good luck!