I think they are totally fine as long as they are used correctly. If you have harsh hands and a super harsh bit, I would say rethink your choices. But I ride my mare in a d-ring slow twist, and she goes great in it. It is all about finding the bit that your horse does well in. I would say make sure your horse is good in the bit, and have relatively soft hands depending on the bit. If your horse goes well in the bit, you shouldn’t have to be all up in his face.