If you are trying to build a database or learn a new function on a spreadsheet, then having a poorly written tutorial means you will not be able to learn. I have discovered the is a good use for poorly written tutorials: artwork!
I have read and attempted hundreds of Photoshop tutorials and there is always some point where the tutorial goes off the rails and stops making sense. Some of my best art pieces came from when I had to give up on the tutorial and go my own way.
http://surlana.deviantart.com/art/Prize-Fight-123024670 <–everyone has done this tutorial but none of them put robots in the picture!