The reason that I say YouTube recommendation system usually OVER saying algorithm, is that algorithm makes it seem like some mysterious force.
It's a reframing. The YouTube Recommendation System, is the same thing it's what most people call the algorithm. But algorithm makes it sound like, you put a video out and then the algorithm's job is to find it some views.
When the opposite is true (this is from Neal Mohan himself (CEO of YouTube). YouTube is a viewer first platform, meaning that it's goal is when a user shows up to give it the BEST content possible to keep that viewer on the platform for the longest time. So. if your video happens to be that viewers favorite video, then hooray! But if not, it's not the "algorithm's" fault, it's that either
A) It doesn't know who your audience is, and is trying to figure it out or (SEO)
B) Your target audience didn't like the way you packaged your video (Thumbnail/Title), compared to other people in the niche.
The reason that I like framing it this way, is it puts the power back in your hands as the creator to improve on these things, small tweaks, testing, trying out new stuff rather than chalking things up to the mysterious algorithm and posting the same thing over and over, and hoping for different results.
That would be insane.