YT competes with premium video content streamers like Netflix, music streamers like Spotify, live streaming like Twitch, and social media like TikTok.
So much so that once I got Youtube Premium, I cancelled two streaming services after realizing how much we watch it.
That's exactly my point. For YouTube-type, independent creators and instructional content, there is no substitute. If you want to watch a drama or comedy, you have a lot of options. This is not scientific, but I know an increasing number of people who don't watch "traditional" media at all and look entirely to YouTube for something to watch, especially if they prefer non-fiction.
How is that different from a monopoly, other then arguing semantics?