I don't know who thought this was a good user experience, because it's one of the most frustrating features I've ever had to deal with. I'm german, but almost all of the things I watch are in english. So usually I will just ignore recommendations with german titles. Except I can't do that anymore, because there's no guarantee that youtube didn't randomly decide to translate the title of an english video into german. And recently, they've added auto-translated audio, which is even worse, because now I'm opening an english video and a terrible robotic german voice is talking to me and I manually need to switch to the original source.
It's also not consistent behavior. It's not like all videos on the front page are looking like they're in german. It's just some of them and afaik there's no way to tell.
And you genuinely can't turn it off completely. Incredibly frustrating and I'm just puzzled by the thought-process that lead to this decision. This would be a pretty cool feature if it was consistently applied and freely configurable.