The sponsor ads work when they're neatly aligned aligned with the video's concept. It wouldn't budge me to see a manufacturer sponsor a PC build video where one of their products are being used. Or channels like GradeA where they advertise the sponsors in a similar way to their vids.
What breaks it is when you can feel the ad clearly feels like a last minute insert (which it feels like almost all the time). Even the bigger creators out there do this.