This is seeing the survivors. Even if there are 100 new big YouTube channels per year for some saturated niche. That number might practically speaking basically mean zero if 10 million people every year earnestly try to succeed in that niche. The hit rate on this example is 1 in 100K.
In the past the only way to do that was to get the backing of these massive capital pools, and dance when and where they say dance, all to get a little trickle down to that artist. Even if that fame resulted in fortune, it was still the smallest piece of the pie.
When someone has X subscribers paying $Y/month directly to them, with fairly low overhead costs of their content creation, they simply aren't going to be in other parts of the workforce and definitely aren't going to be begging labels, because its good enough for most for the time being.
So it doesn't really matter about the saturation in the same way you assumed.
The question was whether any artist can become a massive success without a record label. 10 years ago this didn't even make sense to ask. Today, I can almost believe it.