The Seller Hub is being rolled out to everyone and is here to stay, you can return to the Classic but I don't think it's permanent, also many options and features are being removed, so not a good overview to use.
It does take a bit of getting used to, as it is so different. It has some great features, for example, you can send offers to watchers. Also going top right to Customise you can select the columns of information you do , and do not wish to see on your homepage. It becomes less cluttered, and easier to navigate around.
If you do still wish to revert back, then from the link Customise, bring the Selling Tools column to your homepage. At the bottom is a link Opt Out of The Seller Hub.
If that is not present, then again from Selling Tools, click on Go To My eBay >> Selling. That brings you to the Classic site, you can bookmark it, add it to Favourites, and use that, when you wish to access eBay.
Use a desktop browser, Chrome or Firefox are both eBay friendly, and not an app to manage all of the above.
