There’s a significant aspect of scale being ignored when you talk about video sites before Youtube took off.
Not a single one of those self hosted sites had anywhere near the storage that youtube allows. Want a video from over a year or two ago? Hope you downloaded it or the creator loved it enough to leave it up. Frame rates? Resolution? What are those? I understand that tech has advanced as well, and those issues would not be as severe now, but I really doubt that a lot of channels even now would be able to keep the same lengthy back catalog of old content if they were self hosting.
I also think that there are countless channels that would never have existed if the creators had to figure out hosting their own site, setting up streaming of the video files on it, potentially managing their own comments plugins, potentially managing their own methods to keep viewers aware when new content was posted, and having to somehow spread the word of their existence without the aid of an existing platform trying to keep people viewing things for more ad impressions.
The monopoly of Youtube is a problem, the lack of easy to use and configure open alternatives is a problem… but we can’t ignore the massive impact Youtube had in lowering the barrier to entry and upkeep costs of being a content maker.
There are a lot of hurdles to content creation and hosting that Youtube enables creators to completely ignore.