Soooooo much misunderstanding up above, so let me see if I can clear some stuff up:
1) COPPA is not a group or person. "COPPA" isn't doing anything to anyone. COPPA is the name of an American law aimed at protecting the privacy of children under 13. It has been in effect for nearly 20 years. Google and Youtube have been violating the law for a long, long time and are finally falling into line. It is a law with a valid, important purpose and not at all "stupid".
2) You will not get fined if you mark your content as "not for kids" and it ends up being for kids. If you have a cubing channel and mark it as "not for kids", you're good to go. The problem arises if you mark it "ok for kids" and then publish content that isn't OK for kids. That's where the $42,500 fines come from. Even then, the likelihood of actually getting hit with the fine is really, really small. Mostly what will happen is that Youtube, through their AI, will automatically flag you video as not for kids and that will be that.
3) The disabling of comments on videos for kids is not to protect from bullying. Well, that's maybe 1% of it. The main purpose is to stop the comment sections of videos from being used by predators seeking victims. Currently, the comment sections at Youtube are a haven for gross behavior of that nature.
4) The main effect of this law will be a reduction in ad revenue for a lot of channels. A major effect of COPPA is to make targeted advertising impossible for many demographics. This is because, before the enforcement of the COPPA law, advertisers were (illegally) using the private information of children under 13 (like browsing history, internet searches, etc) to deliver personalized ads. That won't happen anymore. So the ads displayed will be much more generic and, therefore, far less valuable. So, less ad money for channels that are monetised.
For the most part, this is going to be much ado about nothing. There will still be tons of cubing channels putting out content.