Rotary engine’s biggest problem has always been reliability. That’s just an engineering problem at this point since we know the concept is sound.
Regarding using petrol vapor instead of atomized injected fuel it’s very true that combustion would be much more efficient- due to higher compression and less waste of fuel. However, I think the reason this hasn’t been done in a realistic production engine is that gasoline doubles as a cooling agent for the combustion chamber which helps control ignition timing and prevents the cylinder head from melting which could happen otherwise.
That sounds like an engineering challenge — provide more effective cooling at the cylinder head.