The spade bit is NOT a harsh bit. It is used for professional, COMPLETELY broke horses, and the rider doesn't even have to /breathe/ to get the horse to do what they want. When it is done right, it is almost like the horse reads the rider's mind, going exactly where they want with no cue.
But it's not for beginners. It's not even for most 'trainers'. It is an art, and do not knock the bit for being 'harsh'. A snaffle can be terrible harsh in the wrong hands, too.