Someone watching lots of DIY home repair videos will start seeing more. In that case it seems like it's incentivizing good behavior. Likewise, someone watching lots of soft porn on YouTube will be recommended more soft porn.
The algorithm isn't responsible for helping you make good life choices. The algorithm is responsible for recommending videos that you would like, and it seems like it does a good job of that, generally.
Unfortunately, some people like bad things and that's an age old problem that is hard to fix.
That said, it would be nice if users could CTOA (choose their own algorithm) instead of letting Google be the sole gatekeeper.
Likewise the YouTube algorithm helps many people, but criminals or unwanted people (like pedophiles) can also use it.
It's ok to think about ways to prevent it, but I don't think it should be the first concern. Imagine outlawing telephony, because criminals could benefit from its use.