OP is talking about culture rather than technology. Two people both on youtube see entirely different content. Both people will have their own set of big famous creators in their bubble and have never heard of the other persons famous youtubers.

I can see that, but to me it's more about the fact that there just didn't used to be that much content.

True but that’s how the web always was. I don’t see it as a change. In the 90s if you found some niche community most likely no one else knew about it.