Removing the source of the recommendation from your history works a lot more reliably. Sometimes the "Not interested" button will allow you to say "I don't want recommendations based on <X> videos", but they're in denial about how that's the only thing their recommendation engine does, so the option isn't always there.
You mean like incognito mode on Chrome? Unfortunately I like most of the bubble I've built for myself of Youtube. It sucks when my recommendation stream of mostly educational videos from smart, quality-driven DIYers and educators gets overwhelmed with 5 Minute Crafts type garbage because I put on one "oddly satisfying compilation" to run in the background while playing boardgames with friends or something.
