In a few weeks, 1% of creators already using YouTube Studio will no longer see the ‘back to Classic’ button – you’ll be notified 1st & can still access Classic features you need! This won’t apply to everyone else until early next year. More info → https://yt.be/help/a7mG
The new one looks nicer, but navigation is easily much worse and trickier to do with the beta version. Please just keep classic an option to easily use, even let us keep it by default instead of having to switch all the time. Listen to the folks that are giving criticism please