The problem is that big creators have many subscribers, because they're the only ones making videos people want to watch.
If a channel has 100 subscribers - (except if it's a brand new channel) - it's because people saw the videos and decided, no, I don't want to see this, I'm not going to subscribe.
Put all of those people on a platform together, you will just end up with a platform with more creators than viewers.
So? Why is that a problem? My wife occasionally watches this old lady who's vlogged every day for over 14 years straight. She averages 150-200 views. The people who try to build a brand end up getting outsized attention so it seems like that must be what anyone would want, but most people actually aren't trying to do that.
Well, do you want a platform people watch videos on, or a platform people simply upload videos to, never to be seen?
It's not an either-or, but generally speaking, a platform centered around getting more people to watch is probably worse to have in the world than one centered around people just expressing themselves to a handful of e.g. family/friends/small communities. Especially if the former is really just a conduit for ads.