One of my past times is looking up anime opening reactions for fun/to hear people listen to bands I enjoy that sometimes do anime ops, searching that is so scary, you see the same 4 people or every month or so you get 1 or get 1 removed, you can't tell me there's not more than 4 people on the internet that upload opening reactions... when anime is a billion+ dollar industry, if you know particular channels you can see daily uploads on plenty of channels, that are simply search banned for whatever reason by the algorithm.

But yeah, the most outrageous one is older videos, I do believe the reason is that they are using some long term cloud storage that is cheaper for older videos so they removed the ability to search by date.

Additionally, I don't believe the API fully fixes it, because Bing has a wrapper for youtube and searches do not really vary