In sportsman racing the Kawasaki and Suzuki engines are legendary. A mix of early and later KZ parts makes a potent race combo, they say the Suzuki is a close copy of the KZ engine.
I think it's a lot like the Chevrolets and Chrysler hemi's, decades of development have gone into them and they are popular enough that a lot of parts are available. If someone spent the development money on another platform, it might compete as well but NHRA seems to bend the rules towards the sponsor.
Before NHRA adjusted the rules, the V twin guys had to hold all Harley races so they could compete with each other. I'd like to see Kawasaki or Honda make an effort but it would cost a lot and then you have to the possibility of getting ruled out of competition by the book.
Someone besides Vance and Hines would need to develop a competing platform. They have done a pretty good job of selling parts to other teams to compete against themselves, (except Harley stuff, they kept it in house)