I'm not sure how kids factor into this, I've always heard the YouTube rabbit hole in the context of pushing people to either ends of the political spectrum.
As far as "do no harm" goes, implementing safeguard against the alleged rabbit hole has a very strong potential to do harm by making YouTube a partisan platform. Bear in mind that concern over the alleged rabbit hole is not equal between liberals, centrists, and conservatives. Many of the recommended videos I've seen people reference as evidence of the alleged rabbit hole are videos I'd considered mainstream. What it takes to placate the critics has very strong potential to violate the principle of "first, do no harm".
I would suggest looking through that previous link regarding examples of where one can quickly end up in white nationalist content through recommendations. Again, recommendations are for Youtube's own growth-related ends. However, it is emphatically a choice to have them.
Your medium post is not directly related to what I was referring to in my first comment. Yes, bad actors game the recommendation algorithms to troll people. That's what Elsagate was about. People deliberately making channels and videos that would appear as and presumably get recommended as kid friendly content when it was actually shock content. I'm well aware that recommendation algorithms can be abused. Perhaps I should have more strongly emphasized that my examples are presented in a very simplified scenario, that is limited to the alleged political rabbit hole and not things like Elsagate.
The point I am making is that pointing out the fact that it's possible to get to the extremes of YouTube by clicking through on recommended videos shouldn't be surprising. In fact, of you couldn't so that it would be evidence of deliberately trying to keep certain content from being popular.
The question of how well YouTube polices it's terms of service (which already does prohibit hate speech) is related to this question about the alleged rabbit hole because such content presumably exists at the edge of my hypothetical political spectrum values. But it's not directly related to the fact that clicking through on recommended links can bring people to 1 and 10 even if they start at 5 should not be surprising.
As far as "do no harm" goes, implementing safeguard against the alleged rabbit hole has a very strong potential to do harm by making YouTube a partisan platform. Bear in mind that concern over the alleged rabbit hole is not equal between liberals, centrists, and conservatives. Many of the recommended videos I've seen people reference as evidence of the alleged rabbit hole are videos I'd considered mainstream. What it takes to placate the critics has very strong potential to violate the principle of "first, do no harm".