This argument doesn't really hold when you're discussing a monopoly/social network.
Referring to youtube as "just a private company" or "just a video hosting service" is almost to the point of being disingenuous. There are no alternatives that come even close to what youtube offers. You can't just replicate a social network, and even if you could, who has the hardware and resources to do what youtube does?
Vimeo is niche/specialized, it's not for general video uploads. Selfhosting via e.g. Peertube only really works in smallish communities, due to hardware limitations and word of mouth discovery. No other service has the social aspect that youtube does.
The reality is that this is a much more complicated discussion than "oh, merely switch to another private company".
> I swear, it's like people have never had to cancel a newspaper subscription before
This is such a blithe comment that I'm not sure if you actually use youtube to any degree. It is -the- place to put videos and content. Nowhere else has the sheer amount of educational content, etc, all in one place. There's an extreme wealth of content that is not replicated anywhere else on the internet, much less spread across random websites.
Youtube not only allows for discovery via topics/related youtubers, but it also incentivizes people to make content due to income both internally on youtube and externally as they build a brand. I'm not trying to be a shill here, but without youtube I wouldn't have been able to learn about topics like woodworking, chess, bass guitar, music theory, cooking, programming, etc, to the degree that I have , and discover great content makers as well. Not to mention discovering music that isn't necessarily on spotify/etc.
So it's not so easy as to say "just use a different site/company/etc". What site...?