Spot on. If you build a more efficient engine P&W, GE, Honeywell, and a few other companies would be clawing eachothers' eyes for the chance to buy you out.
Boeing and other airframe mfgs would throw you a huge contract immediately if they thought you could actually build the engines and deliver them.
Even if you just build an engine on-par with everybody else. Or even just a bit sub-par. Not everybody wants or able or have use case for those large top of the line very efficient and very expensive engines from the top manufacturers. You can check out the global international drama during the last few years around Ukrainian Motor-Sich engine manufacturer - one of the main engine manufacturers from the USSR times. There are just too few of those engine manufacturers, even if sub-par, around for the current world demand. Anybody wanna make a startup for the engines, initially for UAS market? It is going to blow up after the war as drones have been showing their future dominance. And just look at that beauty (uses the Motor-Sich engines as Turkey don't have their own) https://en.wikipedia.org/wiki/Baykar_Bayraktar_Ak%C4%B1nc%C4... .
Boeing and other airframe mfgs would throw you a huge contract immediately if they thought you could actually build the engines and deliver them.