I mean it is related to the creator and therefore to the video. An option to disable it would be nice, but I dont think this is as bad as watching actual ads
"a notice or announcement in a public medium promoting a product, service, or event or publicizing a job vacancy. "
I'm not sure if a link can be considered an announcement, but otherwise based on the definition I would say it's a gray area and could be argued either way.
Although I would tend to say it isn't an advertisement but a link to one.
Except one is a separate box, has images and is visible whenever (usually hidden due to the description being collapsed) Over all it just takes up extra space, is stuffed in my face and advertises a product