Eh, I don't think you can blame YT on this, or necessarily that there is blame to be had, I'm not sure it's a bad thing.
From YT's perspective it's realistically impossible to review every video uploaded and make sure it complies with law before they publish it.
So yeah, asking the content producer to declare if the video is for kids or not for kids then that's reasonable to me.
The whole "if it's actually directed to kids according to the ftc's view" is clearly to stop people just marking their pedo-gathering videos ("challenges" etc, search the news if you don't know) not for kids to bypass the restrictions but still target them at kids. By necessity this probably does have to be a very wide open to interpretation definition not something you can put into some specific checklist of (anti-)requirements.
The only thing I would perhaps question is if Youtube could not have made it so that if videos were NOT marked as kid friendly then one has to login and age-verify to view the video, but again they would be absolutely slammed by viewers and producers (and probably advertisers) if they did that.
They, Youtube, are stuck between a rock and many hard places, if they do nothing FTC hammers them, if they do this producers complain and might maybe (but extremely unlikely) find themselves unintentionally in trouble, if they took an even harder line everybody complains AND the FTC could come down on them when kids bypass age verification.
Sometimes I think people need to remember Youtube is a business, not a charity or a public service. They got to make a buck while not doing things that will bring undue risk to their business and shareholders.