I don’t see it as a waste of time, you are challenging yourself and the lumber is freely available. I had some pieces of birch that were rotten and punky. I used some wood hardener on the top and bottom fo the piece to solidify it enough for the center and chuck. It was so punky that I had to use sandpaper to give it any kind of smooth surface. Sandpaper is just a tool, like any other. If that is what you need to shape and smooth, don’t be afraid to use it. Nice turning you came up with. If you experience much tearout, try your hand at a natural edge. It helps keep the piece consistent and the tearout, when smoothed, fits in with the overall design.
-- There is little that is simple when it comes to making a simple box.