I got tired of the Mac theme for ubuntu and decided to get rid of it (also realised that Ubuntu needs to be unique and not look like a mac clone!). So after mucking around with the settings for a while and finding that it’s not easy to undo the damage, I started searching online. That’s when I came across this post and the idea is so simple that I wondered why I didn’t think about it to begin with. Take a look, it’ll reset your ubuntu gnome desktop to ‘factory settings’ :).
Update: As mentioned by A Y Siu in the comments, it would be safer to rename your folders using mv rather than delete them flat out.