For one thing, COPPA was introduced in 1998, well before Youtube.
Youtube was collecting information on children so they can target them with ads.
And Youtube has actually been pushed as a platform by which advertisers can exploit an audience of children.
The problem with youtube right now is that they have been encouraging content creators illegally to target children with their content. Youtube is now being forced into complying with the law and content creators, who are a part of the youtube economy, are no longer able to reap the rewards any longer. The content creators were misled, yes, but that isn't justification for allowing Youtube's shit to continue.
And while channels, such as Pewdiepie can claim that they're not made for children, it's clear that their content appeals primarily to children. These sorts of channels that skirt the law need to be forced to comply. While not as serious, it's basically the same sort of problem as companies and individuals who evade taxation by misclassifying their assets (i.e. classifying a hotel as rental property).
Yes, there are content creators who won't be making as much. But that's on Google. It's not like they haven't had 6 years to adjust their Youtube platform.