It's like inventing a new mouse trap, the pests are still with us after a zillion fancy types of mouse traps been invented but the good old wood Spring .50c trap does the job! Two things will always hold back new engine designs, reliability and resale, the latter often the biggest issue!
Sometime ago there was an RV8 for sale (in the States) that had an oddball rotary donk in it, sat on the market for ages, finally sold for peanuts and re-engined wth a proper A/C engine, it's value would have increased instantly!