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
I'd understand if the new studio was much better than the old one and was loaded with features, but it's not. Everything was much easier to get to in classic and the new studio doesn't offer anything new.