They're only useless in that they aren't displayed for your peers, but that was always the least-useful function.

Being able to see a counter that reads as "Twenty-three thousand other people also didn't like this video!" doesn't serve me in any meaningful way; I don't go to Youtube to seek validation of my opinion, so that counter has no value to me. (For the same reason, the thumbs-up counter also has no value to me.)

But my ratings remain useful in that the algorithm still uses the individualized ratings I provide to help present stuff that I might actually want to watch.

As we all know, investors and advertisers love growth; Youtube thrives and grows and gathers/burns money fastest when more people use it more. The algorithm is designed to encourage viewership. Viewership makes number go up in the ways that the money-people care about.

Presenting stuff to me that I don't want to watch makes the number go up -- at best -- slower. The algorithm seeks to avoid that situation (remember, number must only go up).

Personally rating videos helps the machine make number go up in ways that benefit me directly.

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Try to think of it less like a rating of a product on Amazon or of an eBay seller; try not to think of it as an avenue for publicly-displayed praise or admonishment. It's not that. (Maybe it once was -- I seem to recall thumbs-up and thumbs-down counts being shown under each thumbnail on the main feed a million years ago. But it is not that, and it has not been for quite a long time.)

Instead, think of it as one way in which to steer and direct your personalized recommendation algorithm to give you more of the content you enjoy seeing, and less of what you're not as fond of.

Use it as a solely self-serving function in which you push the buttons to receive more of the candy you like, and less of of the candy that you don't like.