Fair enough, I suppose it depends on how broad your categories are.

Personally, I absolutely consider YouTube a video-based social network. You follow people/brands, have at timeline, can contribute comments on what they post, etc.

It doesn't tend to have as broad a social graph as something like FB, but almost nothing does. Twitter (for example) also has a large number of popular public accounts, similar to YouTube.

Facebook and Twitter mostly do not subsidize content creation, but YouTube and TikTok definitely do. That's why I think TikTok will have more staying power.