Personally, I think it’s 100% fine it just depends on the situation! If the horse is very sensitive and prefers a hackamore over a bit, than for sure. However, I personally only like it when more experienced riders use one(and a rider with very light hands). It would just be too easy to hurt the horse if the rider caught them in the mouth or pulled too much to the jump.
It depends on the horse. If the horse is very sensitive in the mouth and rides better in a hackamore then definitely. If your horse responds to a bit with no problems then you can use that. Whatever suits your horse and allows them to go the best they can will be the way to go.