Truthfully, it's all because of Shedinja that it's never a good idea to not have any Fire, Flying, Rock, Ghost, or Dark-type attacks in your arsenal. An ability that bypasses Wonder Guard, a move that suppresses Wonder Guard, or a status move or condition that can deliver indirect damage cannot be ignored either. If Shedinja never existed, however, then this issue would not exist either.
Yes, seeing Shedinja is very unlikely, considering how mediocre its offense is, but if you're not prepared for it, then expect a forfeit to happen.